Bump com.puppycrawl.tools:checkstyle from 10.20.1 to 10.21.0 (#12333)

Bumps [com.puppycrawl.tools:checkstyle](https://github.com/checkstyle/checkstyle) from 10.20.1 to 10.21.0.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](checkstyle/checkstyle@checkstyle-10.20.1...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] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

build.gradle

@@ -396,7 +396,7 @@ dependencies {
     // recommended by https://github.com/wiremock/wiremock/issues/2149#issuecomment-1835775954
     testImplementation 'org.wiremock:wiremock-standalone:3.10.0'
 
-    checkstyle 'com.puppycrawl.tools:checkstyle:10.20.1'
+    checkstyle 'com.puppycrawl.tools:checkstyle:10.21.0'
     // xjc needs the runtime as well for the ant task, otherwise it fails
     xjc group: 'org.glassfish.jaxb', name: 'jaxb-xjc', version: '3.0.2'
     xjc group: 'org.glassfish.jaxb', name: 'jaxb-runtime', version: '3.0.2'