Bump io.reactivex.rxjava3:rxjava from 3.1.7 to 3.1.8 (#493)

Bumps [io.reactivex.rxjava3:rxjava](https://github.com/ReactiveX/RxJava) from 3.1.7 to 3.1.8.
- [Release notes](https://github.com/ReactiveX/RxJava/releases)
- [Commits](ReactiveX/RxJava@v3.1.7...v3.1.8)

---
updated-dependencies:
- dependency-name: io.reactivex.rxjava3:rxjava
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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gradle/libs.versions.toml

@@ -81,7 +81,7 @@ renovateTrigger-gjf = { module = "com.google.googlejavaformat:google-java-format
 
 replaying-share-kotlin = { module = "com.jakewharton.rx2:replaying-share-kotlin", version.ref = "replayingShareKotlin" }
 rx-android = "io.reactivex.rxjava3:rxandroid:3.0.2"
-rx-java = "io.reactivex.rxjava3:rxjava:3.1.7"
+rx-java = "io.reactivex.rxjava3:rxjava:3.1.8"
 rxjava3-bridge = { module = "com.github.akarnokd:rxjava3-bridge", version.ref = "rxjava3Bridge" }
 rxrelay = { module = "com.jakewharton.rxrelay2:rxrelay", version.ref = "rxrelay" }
 test-androidExtJunit = "androidx.test.ext:junit:1.2.0-alpha01"