Remove support for attribute event listeners.

client/dom/generated/src/frog/Notification.dart

 
 class Notification native "Notification" {
 
   String dir;
 
-  EventListener onclick;
-
-  EventListener onclose;
-
-  EventListener ondisplay;
-
-  EventListener onerror;
-
   String replaceId;
 
   void addEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   void cancel() native;
 
   bool dispatchEvent(Event evt) native;
 
   void removeEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   void show() native;
 
   var dartObjectLocalStorage;
 
   String get typeName() native;
 }