Fixes commons-app#1250 Removed creation of multiple instances of Notification activity

Author: Jatin0312

app/src/main/java/fr/free/nrw/commons/notification/NotificationActivity.java

@@ -95,6 +95,7 @@ private void setAdapter(List<Notification> notificationList) {
 
     public static void startYourself(Context context) {
         Intent intent = new Intent(context, NotificationActivity.class);
+        intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
         context.startActivity(intent);
     }
 }