LibWeb: Implement Element.removeAttributeNS

Author: https://github.com/shannonbooth
Commit: 3910efb80b
Pull-request: https://github.com/SerenityOS/serenity/pull/22748
Reviewed-by: https://github.com/ADKaster ✅

Userland/Libraries/LibWeb/DOM/Element.h

@@ -112,6 +112,7 @@ public:
 
     void append_attribute(Attr&);
     void remove_attribute(FlyString const& name);
+    void remove_attribute_ns(Optional<FlyString> const& namespace_, FlyString const& name);
 
     WebIDL::ExceptionOr<bool> toggle_attribute(FlyString const& name, Optional<bool> force);
     size_t attribute_list_size() const;