Rollup merge of rust-lang#129263 - apiraino:add-missing-compat-note, r=cuviper

Add a missing compatibility note in the 1.80.0 release notes

rust-lang#99969 missed being included in the release notes. As discussed [on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/241545-t-release/topic/.2399969.20missed.20the.20release.20notes/near/463002451).

(the discussion about the _a posteriori_ breakage the ecosystem is experiencing is another topic)

Thanks

r? `````@rust-lang/release`````

Author: GuillaumeGomez

RELEASES.md

@@ -143,6 +143,8 @@ Compatibility Notes
 - [Turn `proc_macro_back_compat` lint into a hard error.](https://github.com/rust-lang/rust/pull/125596/)
 - [Detect unused structs even when implementing private traits](https://github.com/rust-lang/rust/pull/122382/)
 - [`std::sync::ReentrantLockGuard<T>` is no longer `Sync` if `T: !Sync`](https://github.com/rust-lang/rust/pull/125527) which means [`std::io::StdoutLock` and `std::io::StderrLock` are no longer Sync](https://github.com/rust-lang/rust/issues/127340)
+- [Type inference will fail in some cases due to new implementations of `FromIterator for Box<str>`.](https://github.com/rust-lang/rust/pull/99969/)
+  Notably, this breaks versions of the `time` crate before 0.3.35, due to no longer inferring the implementation for `Box<[_]>`.
 
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