refactor: declare gin::Wrapper subclasses as final (#43565)

As per the gin docs: "Wrappable<T> explicitly does not support further
subclassing of T. Subclasses of Wrappable<T> should be declared final."

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Charles Kerr <charles@charleskerr.com>

shell/common/gin_helper/event.h

@@ -23,8 +23,8 @@ class ObjectTemplate;
 
 namespace gin_helper::internal {
 
-class Event : public gin::Wrappable<Event>,
-              public gin_helper::Constructible<Event> {
+class Event final : public gin::Wrappable<Event>,
+                    public gin_helper::Constructible<Event> {
  public:
   // gin_helper::Constructible
   static gin::Handle<Event> New(v8::Isolate* isolate);