Bump maven-site-plugin from 3.9.0 to 3.9.1 (#708)

Author: dependabot[bot]

pom.xml

@@ -94,7 +94,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-site-plugin</artifactId>
-          <version>3.9.0</version>
+          <version>3.9.1</version>
         </plugin>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>