Bump io.reactivex.rxjava3:rxjava from 3.1.6 to 3.1.8

Bumps [io.reactivex.rxjava3:rxjava](/~https://github.com/ReactiveX/RxJava) from 3.1.6 to 3.1.8.
- [Release notes](/~https://github.com/ReactiveX/RxJava/releases)
- [Commits](ReactiveX/RxJava@v3.1.6...v3.1.8)

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

Signed-off-by: dependabot[bot] <support@github.com>

amazon-kinesis-client/pom.xml

@@ -111,7 +111,7 @@
     <dependency>
       <groupId>io.reactivex.rxjava3</groupId>
       <artifactId>rxjava</artifactId>
-      <version>3.1.6</version>
+      <version>3.1.8</version>
     </dependency>
 
     <dependency>