LibWeb/HTML: Use finalize to clean up MessagePort instances

Author: https://github.com/shannonbooth
Commit: e767029e24
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3070
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/konradekk

Libraries/LibWeb/HTML/MessagePort.h

@@ -68,6 +68,7 @@ private:
     explicit MessagePort(JS::Realm&);
 
     virtual void initialize(JS::Realm&) override;
+    virtual void finalize() override;
     virtual void visit_edges(Cell::Visitor&) override;
 
     bool is_entangled() const;