Add warning for create and trigger event upgrade example (#35612)

* Add warning for create and trigger event upgrade example

* Update index.md

---------

Co-authored-by: Hamish Willee <hamishwillee@gmail.com>

files/en-us/web/events/creating_and_triggering_events/index.md

@@ -56,7 +56,7 @@ The older approach to creating events uses APIs inspired by Java. The following
 const event = document.createEvent("Event");
 
 // Define that the event name is 'build'.
-event.initEvent("build", true, true);
+event.initEvent("build");
 
 // Listen for the event.
 elem.addEventListener(