Bump maven-site-plugin from 3.7.1 to 3.9.1

Bumps [maven-site-plugin](https://github.com/apache/maven-site-plugin) from 3.7.1 to 3.9.1.
- [Release notes](https://github.com/apache/maven-site-plugin/releases)
- [Commits](apache/maven-site-plugin@maven-site-plugin-3.7.1...maven-site-plugin-3.9.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pom.xml

@@ -473,7 +473,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-site-plugin</artifactId>
-          <version>3.7.1</version>
+          <version>3.9.1</version>
           <configuration>
             <skipDeploy>true</skipDeploy><!-- don't deploy site with maven-site-plugin -->
           </configuration>