LibCore: Remove unused CustomEvent

Author: https://github.com/awesomekling
Commit: aec1f6aa7e
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5817
Reviewed-by: https://github.com/gmta ✅

Libraries/LibCore/EventReceiver.cpp

@@ -31,8 +31,6 @@ void EventReceiver::event(Core::Event& event)
     case Core::Event::Invalid:
         VERIFY_NOT_REACHED();
         break;
-    case Core::Event::Custom:
-        return custom_event(static_cast<CustomEvent&>(event));
     default:
         break;
     }
@@ -42,10 +40,6 @@ void EventReceiver::timer_event(Core::TimerEvent&)
 {
 }
 
-void EventReceiver::custom_event(CustomEvent&)
-{
-}
-
 void EventReceiver::start_timer(int ms)
 {
     if (m_timer_id) {