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

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
io.reactivex.rxjava3:rxjava	3.1.6 -> 3.1.8

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Release Notes

ReactiveX/RxJava (io.reactivex.rxjava3:rxjava)

v3.1.8

Maven
JavaDocs

Bugfixes

• Fix ObservableSwitchMap NullPointerException due to cancel race. (https://github.com/ReactiveX/RxJava/pull/7597)

v3.1.7

Maven
JavaDocs

API changes

• Add onDropped callback for onBackpressureLatest. (#​7542)
• Add onDropped callback to onBackpressureBuffer. (#​7567)

Documentation

• Change summary to caption, because summary is obsolete in HTML5. (#​7534)
• Try using https to access the reactive streams javadoc. (#​7535)
• Improve Javadoc of Disposable.

Other

• Add minimum GitHub token permissions for workflows. (#​7541)
• Create SECURITY.md (#​7546)
• Add copyright and license to jar. (#​7520)
• Convert CompletableOnErrorComplete$onError inner class to static. (#​7575)
• Allow null accumulator type in the collect(Collector) operators. (#​7590)

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