Bump com.puppycrawl.tools:checkstyle from 10.18.1 to 10.21.2 (#249)

Bumps [com.puppycrawl.tools:checkstyle](https://github.com/checkstyle/checkstyle) from 10.18.1 to 10.21.2.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](checkstyle/checkstyle@checkstyle-10.18.1...checkstyle-10.21.2)

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

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

Author: dependabot[bot]

pom.xml

@@ -23,7 +23,7 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <pmd.version>7.10.0</pmd.version>
     <pmd.build-tools.version>29</pmd.build-tools.version>
-    <checkstyle.version>10.18.1</checkstyle.version>
+    <checkstyle.version>10.21.2</checkstyle.version>
     <checkstyle.plugin.version>3.6.0</checkstyle.plugin.version>
     <pmd.plugin.version>3.26.0</pmd.plugin.version>
     <pmd.check.version>7.10.0</pmd.check.version>