chore(deps): update dependency org.apache.maven.plugins:maven-site-plugin to v3.21.0

Author: renovate[bot]

pom.xml

@@ -129,7 +129,7 @@
                 <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
                 <plugin>
                     <artifactId>maven-site-plugin</artifactId>
-                    <version>3.7.1</version>
+                    <version>3.21.0</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-project-info-reports-plugin</artifactId>