LibWeb: Provide a default DOM::EventTarget::dispatch_event()

All EventTarget subclasses except Window do the same exact thing in
their overrides, so let's just share an implementation in the base.

Userland/Libraries/LibWeb/CSS/MediaQueryList.cpp

@@ -37,11 +37,6 @@ bool MediaQueryList::matches() const
     return false;
 }
 
-bool MediaQueryList::dispatch_event(NonnullRefPtr<DOM::Event> event)
-{
-    return DOM::EventDispatcher::dispatch(*this, event);
-}
-
 JS::Object* MediaQueryList::create_wrapper(JS::GlobalObject& global_object)
 {
     return wrap(global_object, *this);