LibJS: Convert WeakMap::create() to NonnullGCPtr

Author: https://github.com/linusg
Commit: 3358ddfd0e
Pull-request: https://github.com/SerenityOS/serenity/pull/16479
Reviewed-by: https://github.com/davidot ✅

Userland/Libraries/LibJS/Runtime/WeakMap.h

@@ -19,7 +19,7 @@ class WeakMap final
     JS_OBJECT(WeakMap, Object);
 
 public:
-    static WeakMap* create(Realm&);
+    static NonnullGCPtr<WeakMap> create(Realm&);
 
     virtual ~WeakMap() override = default;