build(deps): bump org.apache.maven.plugins:maven-site-plugin (#477)

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

pom.xml

@@ -73,7 +73,7 @@
   <org.apache.maven.plugins.compiler.version>3.13.0</org.apache.maven.plugins.compiler.version>
   <org.apache.maven.plugins.toolchains.version>3.2.0</org.apache.maven.plugins.toolchains.version>
   <org.apache.maven.plugins.surefire.version>3.5.1</org.apache.maven.plugins.surefire.version>
-  <org.apache.maven.plugins.site.version>3.20.0</org.apache.maven.plugins.site.version>
+  <org.apache.maven.plugins.site.version>3.21.0</org.apache.maven.plugins.site.version>
   <org.apache.maven.plugins.info.reports.version>3.8.0</org.apache.maven.plugins.info.reports.version>
   <com.mycila.license.maven.plugin.version>4.6</com.mycila.license.maven.plugin.version>