Add tooltip

public/app/plugins/panel/graph/time_regions_form.html

@@ -1,5 +1,5 @@
 <div class="gf-form-group">
-  <h5>Time regions</h5>
+  <h5>Time regions <tip>All configured time regions refers to UTC time</tip></h5>
   <div class="gf-form-inline" ng-repeat="timeRegion in ctrl.panel.timeRegions">
     <div class="gf-form">
       <label class="gf-form-label">T{{$index+1}}</label>