updated wiki location in manual

manual/using.html

@@ -455,7 +455,7 @@ If you need a special function, you should
 <ol>
   <li>have a look at this manual, because Ant provides lot of tasks</li>
   <li>have a look at the external task page <a href="https://ant.apache.org/external.html" target="_top">online</a></li>
-  <li>have a look at the external task <a href="https://wiki.apache.org/ant/AntExternalTaskdefs" target="_top">wiki
+  <li>have a look at the external task <a href="https://cwiki.apache.org/confluence/display/ANT/AntExternalTaskdefs" target="_top">wiki
     page</a></li>
   <li>ask on the <a href="https://ant.apache.org/mail.html#User%20List" target="_top">Ant user</a> list</li>
   <li><a href="tutorial-writing-tasks.html">implement</a> (and share) your own</li>