SL-13824 Remove notification when both joining a group and leaving a group

indra/newview/llviewermessage.cpp

@@ -5036,6 +5036,15 @@ bool attempt_standard_notification(LLMessageSystem* msgsystem)
 		// notification was specified using the new mechanism, so we can just handle it here
 		std::string notificationID;
 		msgsystem->getStringFast(_PREHASH_AlertInfo, _PREHASH_Message, notificationID);
+
+		//SL-13824 skip notification when both joining a group and leaving a group
+		//remove this after server stops sending these messages  
+		if (notificationID == "JoinGroupSuccess" ||
+			notificationID == "GroupDepart")
+		{
+			return true;
+		}
+
 		if (!LLNotifications::getInstance()->templateExists(notificationID))
 		{
 			return false;

indra/newview/skins/default/xui/en/notifications.xml

@@ -4214,13 +4214,6 @@ Leave Group?
      yestext="OK"/>
   </notification>
 
-  <notification
-   icon="notify.tga"
-   name="GroupDepart"
-   type="notify">
-You have left the group &apos;&lt;nolink&gt;[group_name]&lt;/nolink&gt;&apos;.
-    <tag>group</tag>
-  </notification>
 
   <notification
    icon="alertmodal.tga"