docs: remove Google+ link from page footer

Google is shutting down Google+, with no replacement, in the very near
future so we are losing the Libvirt community group there.
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

docs/page.xsl

@@ -175,7 +175,6 @@
             <h3>Community</h3>
             <ul>
               <li><a href="https://twitter.com/hashtag/libvirt">twitter</a></li>
-              <li><a href="https://plus.google.com/communities/109522598353007505282">google+</a></li>
               <li><a href="http://stackoverflow.com/questions/tagged/libvirt">stackoverflow</a></li>
               <li><a href="http://serverfault.com/questions/tagged/libvirt">serverfault</a></li>
             </ul>