Show group wiki settings form when group wiki is licensed

In #208412 (closed) we implemented group wiki visibility settings. During the manual testing, we discovered that, when the user doesn't have the group wiki feature licensed, we still show the group wiki setting section.

In this MR we're fixing that and only showing it when the group feature is licensed.

The behavior is behind a ff (#358387 (closed)) so we don't need to add the changelog trailer.