LibWeb: Port CloseEvent to new String

Author: https://github.com/kennethmyhra
Commit: e661f03ffa
Pull-request: https://github.com/SerenityOS/serenity/pull/17722
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/HTML/CloseEvent.idl

@@ -1,6 +1,6 @@
 #import <DOM/Event.idl>
 
-[Exposed=*]
+[Exposed=*, UseNewAKString]
 interface CloseEvent : Event {
     constructor(DOMString type, optional CloseEventInit eventInitDict = {});