`AsFd` and `AsRawFd` are implemented for `Arc<T>`, but not `Rc<T>`

[ids1024]

I was looking through the list of things that implement AsFd, and noticed there's an implementation for Arc<T> where T: AsFd, but not for Rc. I don't think there's any subtle any subtle reason this couldn't/shouldn't be implemented for Rc too?