fix(deps): update dependency io.reactivex.rxjava3:rxjava to v3.1.8 (#4092)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [io.reactivex.rxjava3:rxjava](https://github.com/ReactiveX/RxJava) |
`3.1.6` -> `3.1.8` |
[![age](https://developer.mend.io/api/mc/badges/age/maven/io.reactivex.rxjava3:rxjava/3.1.8?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
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|
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|
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|

---

### Release Notes

<details>
<summary>ReactiveX/RxJava (io.reactivex.rxjava3:rxjava)</summary>

###
[`v3.1.8`](https://github.com/ReactiveX/RxJava/releases/tag/v3.1.8)


[Maven](http://search.maven.org/#artifactdetails%7Cio.reactivex.rxjava3%7Crxjava%7C3.1.8%7C)
[JavaDocs](http://reactivex.io/RxJava/3.x/javadoc/3.1.8)

##### Bugfixes

- Fix `ObservableSwitchMap` `NullPointerException` due to cancel race.
([https://github.com/ReactiveX/RxJava/pull/7597](https://github.com/ReactiveX/RxJava/pull/7597))

###
[`v3.1.7`](https://github.com/ReactiveX/RxJava/releases/tag/v3.1.7)


[Maven](http://search.maven.org/#artifactdetails%7Cio.reactivex.rxjava3%7Crxjava%7C3.1.7%7C)
[JavaDocs](http://reactivex.io/RxJava/3.x/javadoc/3.1.7)

##### API changes

- Add `onDropped` callback for `onBackpressureLatest`. (<a
href='https://github.com/ReactiveX/RxJava/issues/7542'>[#&#8203;7542](https://github.com/ReactiveX/RxJava/issues/7542)</a>)
- Add `onDropped` callback to `onBackpressureBuffer`. (<a
href='https://github.com/ReactiveX/RxJava/issues/7567'>[#&#8203;7567](https://github.com/ReactiveX/RxJava/issues/7567)</a>)

##### Documentation

- Change summary to caption, because summary is obsolete in HTML5. (<a
href='https://github.com/ReactiveX/RxJava/issues/7534'>[#&#8203;7534](https://github.com/ReactiveX/RxJava/issues/7534)</a>)
- Try using https to access the reactive streams javadoc. (<a
href='https://github.com/ReactiveX/RxJava/issues/7535'>[#&#8203;7535](https://github.com/ReactiveX/RxJava/issues/7535)</a>)
-   Improve Javadoc of `Disposable`.

##### Other

- Add minimum GitHub token permissions for workflows. (<a
href='https://github.com/ReactiveX/RxJava/issues/7541'>[#&#8203;7541](https://github.com/ReactiveX/RxJava/issues/7541)</a>)
- Create SECURITY.md (<a
href='https://github.com/ReactiveX/RxJava/issues/7546'>[#&#8203;7546](https://github.com/ReactiveX/RxJava/issues/7546)</a>)
- Add copyright and license to jar. (<a
href='https://github.com/ReactiveX/RxJava/issues/7520'>[#&#8203;7520](https://github.com/ReactiveX/RxJava/issues/7520)</a>)
- Convert `CompletableOnErrorComplete$onError` inner class to static.
(<a
href='https://github.com/ReactiveX/RxJava/issues/7575'>[#&#8203;7575](https://github.com/ReactiveX/RxJava/issues/7575)</a>)
- Allow null accumulator type in the `collect(Collector)` operators. (<a
href='https://github.com/ReactiveX/RxJava/issues/7590'>[#&#8203;7590](https://github.com/ReactiveX/RxJava/issues/7590)</a>)

</details>

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gradle/libs.versions.toml

@@ -46,7 +46,7 @@ okhttp = "4.11.0"
 retrofit = "2.9.0"
 robolectric = "4.10.3"
 rxandroid3 = "3.0.2"
-rxjava3 = "3.1.6"
+rxjava3 = "3.1.8"
 rxkotlin3 = "3.0.1"
 sparkbutton = "4.2.0"
 touchimageview = "3.5"