Upgrade maven-site-plugin to 3.9.1

Change-Id: I8fd46eef2851d48429b21c543c2441efcb1378fe
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

pom.xml

@@ -341,7 +341,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-site-plugin</artifactId>
-          <version>3.9.0</version>
+          <version>3.9.1</version>
           <dependencies>
             <dependency><!-- add support for ssh/scp -->
               <groupId>org.apache.maven.wagon</groupId>