[1.1.x] Bump io.reactivex.rxjava3:rxjava from 3.1.8 to 3.1.9

Bumps [io.reactivex.rxjava3:rxjava](https://github.com/ReactiveX/RxJava) from 3.1.8 to 3.1.9.
- [Release notes](https://github.com/ReactiveX/RxJava/releases)
- [Commits](ReactiveX/RxJava@v3.1.8...v3.1.9)

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

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

pom.xml

@@ -85,7 +85,7 @@
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <jetty-version>9.4.55.v20240627</jetty-version>
-    <rxjava-version>3.1.8</rxjava-version>
+    <rxjava-version>3.1.9</rxjava-version>
     <spring-version>5.3.37</spring-version>
     <slf4j-version>2.0.14</slf4j-version>
     <log4j2-version>2.23.1</log4j2-version>