Bump org.apache.maven.plugins:maven-site-plugin from 3.12.1 to 3.20.0

Bumps [org.apache.maven.plugins:maven-site-plugin](https://github.com/apache/maven-site-plugin) from 3.12.1 to 3.20.0.
- [Commits](apache/maven-site-plugin@maven-site-plugin-3.12.1...maven-site-plugin-3.20.0)

---
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]>

pom.xml

@@ -31,7 +31,7 @@
         <jxr.version>3.4.0</jxr.version>
         <taglist.version>3.1.0</taglist.version>
         <spotbugs.version>4.8.6.2</spotbugs.version>
-        <m3.site.version>3.12.1</m3.site.version>
+        <m3.site.version>3.20.0</m3.site.version>
         <changelog.version>2.2</changelog.version>
         <changelog.version>2.2</changelog.version>
         <bundle.plugin.version>5.1.9</bundle.plugin.version>