Bump io.reactivex.rxjava3:rxjava from 3.1.8 to 3.1.9 in /start

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:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

start/inventory/pom.xml

@@ -63,7 +63,7 @@
         <dependency>
             <groupId>io.reactivex.rxjava3</groupId>
             <artifactId>rxjava</artifactId>
-            <version>3.1.8</version>
+            <version>3.1.9</version>
        </dependency>
        <!-- end::rxjava[] -->
        <dependency>

start/system/pom.xml

@@ -61,7 +61,7 @@
         <dependency>
             <groupId>io.reactivex.rxjava3</groupId>
             <artifactId>rxjava</artifactId>
-            <version>3.1.8</version>
+            <version>3.1.9</version>
         </dependency>
         <!-- end::rxjava[] -->
         <dependency>