Clarify the documentation for scan operators (#7093)

* Clarify the documentation for scan operators

* Fix typo

Co-authored-by: David Andrews <dta@duolingo.com>

Author: akarnokd

src/main/java/io/reactivex/rxjava3/core/Flowable.java

@@ -14675,10 +14675,9 @@ public final <U> Flowable<T> sample(@NonNull Publisher<U> sampler, boolean emitL
     }
 
     /**
-     * Returns a {@code Flowable} that applies a specified accumulator function to the first item emitted by the current
-     * {@code Flowable}, then feeds the result of that function along with the second item emitted by the current
-     * {@code Floawble} into the same function, and so on until all items have been emitted by the current {@code Flowable},
-     * emitting the result of each of these iterations.
+     * Returns a {@code Flowable} that emits the first value emitted by the current {@code Flowable}, then emits one value
+     * for each subsequent value emitted by the current {@code Flowable}. Each emission after the first is the result of
+     * applying the specified accumulator function to the previous emission and the corresponding value from the current @{code Flowable}.
      * <p>
      * <img width="640" height="320" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/scan.v3.png" alt="">
      * <p>
@@ -14709,10 +14708,9 @@ public final Flowable<T> scan(@NonNull BiFunction<T, T, T> accumulator) {
     }
 
     /**
-     * Returns a {@code Flowable} that applies a specified accumulator function to the first item emitted by the current
-     * {@code Flowable} and a seed value, then feeds the result of that function along with the second item emitted by
-     * the current {@code Flowable} into the same function, and so on until all items have been emitted by the current
-     * {@code Flowable}, emitting the result of each of these iterations.
+     * Returns a {@code Flowable} that emits the provided initial (seed) value, then emits one value for each value emitted
+     * by the current {@code Flowable}. Each emission after the first is the result of applying the specified accumulator
+     * function to the previous emission and the corresponding value from the current @{code Flowable}.
      * <p>
      * <img width="640" height="320" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/scanSeed.v3.png" alt="">
      * <p>
@@ -14763,10 +14761,9 @@ public final Flowable<T> scan(@NonNull BiFunction<T, T, T> accumulator) {
     }
 
     /**
-     * Returns a {@code Flowable} that applies a specified accumulator function to the first item emitted by the current
-     * {@code Flowable} and a seed value, then feeds the result of that function along with the second item emitted by
-     * the current {@code Flowable} into the same function, and so on until all items have been emitted by the current
-     * {@code Flowable}, emitting the result of each of these iterations.
+     * Returns a {@code Flowable} that emits the provided initial (seed) value, then emits one value for each value emitted
+     * by the current {@code Flowable}. Each emission after the first is the result of applying the specified accumulator
+     * function to the previous emission and the corresponding value from the current @{code Flowable}.
      * <p>
      * <img width="640" height="320" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/scanSeed.v3.png" alt="">
      * <p>

src/main/java/io/reactivex/rxjava3/core/Observable.java

@@ -12202,10 +12202,9 @@ public final <U> Observable<T> sample(@NonNull ObservableSource<U> sampler, bool
     }
 
     /**
-     * Returns an {@code Observable} that applies a specified accumulator function to the first item emitted by the current
-     * {@code Observable}, then feeds the result of that function along with the second item emitted by the current
-     * {@code Observable} into the same function, and so on until all items have been emitted by the current {@code Observable},
-     * emitting the result of each of these iterations.
+     * Returns an {@code Observable} that emits the first value emitted by the current {@code Observable}, then emits one value
+     * for each subsequent value emitted by the current {@code Observable}. Each emission after the first is the result of
+     * applying the specified accumulator function to the previous emission and the corresponding value from the current @{code Observable}.
      * <p>
      * <img width="640" height="320" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/scan.v3.png" alt="">
      * <p>
@@ -12232,10 +12231,9 @@ public final Observable<T> scan(@NonNull BiFunction<T, T, T> accumulator) {
     }
 
     /**
-     * Returns an {@code Observable} that applies a specified accumulator function to the first item emitted by the current
-     * {@code Observable} and a seed value, then feeds the result of that function along with the second item emitted by
-     * the current {@code Observable} into the same function, and so on until all items have been emitted by the current
-     * {@code Observable}, emitting the result of each of these iterations.
+     * Returns an {@code Observable} that emits the provided initial (seed) value, then emits one value for each value emitted
+     * by the current {@code Observable}. Each emission after the first is the result of applying the specified accumulator
+     * function to the previous emission and the corresponding value from the current @{code Observable}.
      * <p>
      * <img width="640" height="320" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/scanSeed.v3.png" alt="">
      * <p>
@@ -12282,10 +12280,9 @@ public final <R> Observable<R> scan(@NonNull R initialValue, @NonNull BiFunction
     }
 
     /**
-     * Returns an {@code Observable} that applies a specified accumulator function to the first item emitted by the current
-     * {@code Observable} and a seed value, then feeds the result of that function along with the second item emitted by
-     * the current {@code Observable} into the same function, and so on until all items have been emitted by the current
-     * {@code Observable}, emitting the result of each of these iterations.
+     * Returns an {@code Observable} that emits the provided initial (seed) value, then emits one value for each value emitted
+     * by the current {@code Observable}. Each emission after the first is the result of applying the specified accumulator
+     * function to the previous emission and the corresponding value from the current @{code Observable}.
      * <p>
      * <img width="640" height="320" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/scanSeed.v3.png" alt="">
      * <p>