Bump maven-site-plugin from 3.9.1 to 3.12.1

Bumps [maven-site-plugin](https://github.com/apache/maven-site-plugin) from 3.9.1 to 3.12.1.
- [Release notes](https://github.com/apache/maven-site-plugin/releases)
- [Commits](apache/maven-site-plugin@maven-site-plugin-3.9.1...maven-site-plugin-3.12.1)

---
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

@@ -89,7 +89,7 @@
       <resources.plugin.version>3.2.0</resources.plugin.version>
       <scm.plugin.version>1.11.2</scm.plugin.version>
       <selenium.plugin.version>2.3</selenium.plugin.version>
-      <site.plugin.version>3.9.1</site.plugin.version>
+      <site.plugin.version>3.12.1</site.plugin.version>
       <shade.plugin.version>3.2.4</shade.plugin.version>
       <source.plugin.version>3.2.1</source.plugin.version>
       <surefire.version>3.0.0-M5</surefire.version>