modify username hint

configure_thurvserver.tpl

@@ -282,7 +282,7 @@ var _localLang = {
                                         {$customfields[0].input}
                                         {if $customfields[0].description}
                                             <span class="field-help-text">
-                                                <div class="alert alert-info">
+                                                <div class="alert alert-warning">
                                                     {$customfields[0].description}
                                                 </div>
                                             </span>