LibWeb: Convert create_new_child_navigable to HeapFunction

Author: https://github.com/shannonbooth
Commit: 3a7ccf8c25
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1108
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/HTML/NavigableContainer.h

@@ -64,7 +64,7 @@ protected:
     // https://html.spec.whatwg.org/multipage/iframe-embed-object.html#navigate-an-iframe-or-frame
     void navigate_an_iframe_or_frame(URL::URL url, ReferrerPolicy::ReferrerPolicy referrer_policy, Optional<String> srcdoc_string = {});
 
-    WebIDL::ExceptionOr<void> create_new_child_navigable(JS::SafeFunction<void()> afterSessionHistoryUpdate = {});
+    WebIDL::ExceptionOr<void> create_new_child_navigable(JS::Handle<JS::HeapFunction<void()>> after_session_history_update = {});
 
     // https://html.spec.whatwg.org/multipage/document-sequences.html#content-navigable
     JS::GCPtr<Navigable> m_content_navigable { nullptr };