LibWeb: Make DOM::Event and all its subclasses GC-allocated

Author: https://github.com/awesomekling
Commit: 7c3db526b0
Pull-request: https://github.com/SerenityOS/serenity/pull/14816
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/HTML/PromiseRejectionEvent.idl

@@ -1,6 +1,6 @@
 #import <DOM/Event.idl>
 
-[Exposed=(Window,Worker)]
+[Exposed=(Window,Worker), NoInstanceWrapper]
 interface PromiseRejectionEvent : Event {
     constructor(DOMString type, PromiseRejectionEventInit eventInitDict);