Bump org.apache.maven.plugins:maven-site-plugin from 3.20.0 to 3.21.0

Bumps [org.apache.maven.plugins:maven-site-plugin](https://github.com/apache/maven-site-plugin) from 3.20.0 to 3.21.0.
- [Release notes](https://github.com/apache/maven-site-plugin/releases)
- [Commits](apache/maven-site-plugin@maven-site-plugin-3.20.0...maven-site-plugin-3.21.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -135,7 +135,7 @@
 		<version.org.apache.maven.plugins.release>3.1.1</version.org.apache.maven.plugins.release>
 		<version.org.apache.maven.plugins.resources>3.3.1</version.org.apache.maven.plugins.resources>
 		<version.org.apache.maven.plugins.scm-publish>3.3.0</version.org.apache.maven.plugins.scm-publish>
-		<version.org.apache.maven.plugins.site>3.20.0</version.org.apache.maven.plugins.site>
+		<version.org.apache.maven.plugins.site>3.21.0</version.org.apache.maven.plugins.site>
 		<version.org.apache.maven.plugins.shade>3.6.0</version.org.apache.maven.plugins.shade>
 		<version.org.apache.maven.plugins.source>3.3.1</version.org.apache.maven.plugins.source>
 		<version.org.apache.maven.plugins.surefire>3.5.1</version.org.apache.maven.plugins.surefire>