fix caret for help button is ds http settings

public/app/features/plugins/partials/ds_http_settings.html

@@ -32,8 +32,8 @@
       <div class="gf-form">
         <label class="gf-form-label query-keyword pointer" ng-click="toggleAccessHelp()">
           Help&nbsp;
-          <i class="fa fa-caret-down" ng-show="ctrl.showAccessHelp"></i>
-          <i class="fa fa-caret-right" ng-hide="ctrl.showAccessHelp">&nbsp;</i>
+          <i class="fa fa-caret-down" ng-show="showAccessHelp"></i>
+          <i class="fa fa-caret-right" ng-hide="showAccessHelp">&nbsp;</i>
         </label>
       </div>
     </div>