LibJS: Remove implicit wrapping/unwrapping of completion records

This is an editorial change in the ECMA-262 spec, with similar changes
in some proposals.

See:
- 7575f74
- df899eb
- 9eb5a12
- c81f527

Userland/Libraries/LibJS/Runtime/FinalizationRegistry.cpp

@@ -76,7 +76,7 @@ ThrowCompletionOr<void> FinalizationRegistry::cleanup(Optional<JobCallback> call
         TRY(vm.host_call_job_callback(global_object, cleanup_callback, js_undefined(), move(arguments)));
     }
 
-    // 4. Return NormalCompletion(empty).
+    // 4. Return unused.
     return {};
 }