GC object are already non-extensible ([[IsExtensible]] returns true). Preventing extensions on a non-extensible object should be an no-op.

By returning false to [[PreventExtensions]], any caller to Object.preventExtensions() would get a thrown TypeError even though the object is already non-extensible, which is surprising (even though it is not technically a violation of the object invariants).

To avoid this surprising behavior, WASM Garbage Collected Objects should return true for [[PreventExtensions]].