system: remove duplicated hint

We added the former, but it basically says the same thing.  ;)

src/www/system_hasync.php

@@ -191,7 +191,6 @@ include("head.inc");
                         <lu>
                           <li><?=sprintf(gettext('When using XMLRPC sync to a backup machine running on another port/protocol please input the full url (example: %s)'), 'https://192.168.1.1:444/') ?></li>
                           <li><?=gettext('For setting up the backup machine leave this field empty, and do not forget to allow incoming connections on the specified interface for synchronization.') ?></li>
-                          <li><b><?=gettext('Do not use the Synchronize Config to IP and password option on backup cluster members!') ?></b></li>
                         </lu>
                       </div>
                     </div>