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

Author: renovate[bot]

pom.xml

@@ -350,7 +350,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-site-plugin</artifactId>
-                    <version>3.9.1</version>
+                    <version>3.21.0</version>
                 </plugin>
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
@@ -517,7 +517,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-site-plugin</artifactId>
-                <version>3.9.1</version>
+                <version>3.21.0</version>
                 <dependencies>
                     <dependency>
                         <groupId>org.apache.maven.doxia</groupId>