use request->variable instead of get_super_globals in acp_listener

[RobertHeim]

  $post = $this->request->get_super_global(\phpbb\request\request::POST);
  $prune = isset($post['rh_topictags_prune']) ? $post['rh_topictags_prune'] : 0;

As you only use rh_topictags_prune you don't need the whole array. You should use request->variable instead. This happens in other places in your code as well.