Bump com.puppycrawl.tools:checkstyle from 10.20.2 to 10.21.0 (#277)

Bumps [com.puppycrawl.tools:checkstyle](https://github.com/checkstyle/checkstyle) from 10.20.2 to 10.21.0.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](checkstyle/checkstyle@checkstyle-10.20.2...checkstyle-10.21.0)

---
updated-dependencies:
- dependency-name: com.puppycrawl.tools:checkstyle
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

pom.xml

@@ -76,7 +76,7 @@
     <formatter.plugin.version>2.24.1</formatter.plugin.version>
 
     <maven.checkstyle.version>3.6.0</maven.checkstyle.version>
-    <checkstyle.version>10.20.2</checkstyle.version>
+    <checkstyle.version>10.21.0</checkstyle.version>
 
     <!-- A dynamic argument that can be used by CI when releasing a new version -->
     <revision>0.0.0-SNAPSHOT</revision>