Bump org.apache.maven.plugins:maven-checkstyle-plugin

Bumps [org.apache.maven.plugins:maven-checkstyle-plugin](https://github.com/apache/maven-checkstyle-plugin) from 3.3.1 to 3.4.0.
- [Commits](apache/maven-checkstyle-plugin@maven-checkstyle-plugin-3.3.1...maven-checkstyle-plugin-3.4.0)

---
updated-dependencies:
- dependency-name: org.apache.maven.plugins:maven-checkstyle-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

pom.xml

@@ -25,7 +25,7 @@
         <rxjava2.version>2.2.21</rxjava2.version>
 
         <javadoc.version>3.7.0</javadoc.version>
-        <checkstyle.version>3.3.1</checkstyle.version>
+        <checkstyle.version>3.4.0</checkstyle.version>
         <pmd.version>3.22.0</pmd.version>
         <project.info.version>3.5.0</project.info.version>
         <jxr.version>3.4.0</jxr.version>