Wrong default in the "tar" task manual

This closes #107 pull request at github/apache/ant repo

manual/Tasks/tar.html

@@ -126,7 +126,7 @@ to <q>gzip</q>, <q>bzip2</q>, or <q>xz</q>.</p>
     <td>compression</td>
     <td>compression method.  Allowable values are <q>none</q>, <q>gzip</q>, <q>xz</q>
       and <q>bzip2</q>.</td>
-    <td>No; default is <q>warn</q></td>
+    <td>No; default is <q>none</q></td>
   </tr>
   <tr>
     <td>encoding</td>