LibWeb: Make CSSStyleDeclaration GC-allocated

Author: https://github.com/awesomekling
Commit: 72bacba97b
Pull-request: https://github.com/SerenityOS/serenity/pull/14816
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/Forward.h

@@ -459,7 +459,6 @@ class CharacterDataWrapper;
 class CloseEventWrapper;
 class CommentWrapper;
 class CryptoWrapper;
-class CSSStyleDeclarationWrapper;
 class CustomEventWrapper;
 class DocumentFragmentWrapper;
 class DocumentTypeWrapper;