Summary:
Deletes `setAndForwardRefs` because it encourages a subtle pitfall with managing the referential equality of `ref` entities.
By the time this commit is landed, there will have been no more call sites to it in the `facebook/react-native` repository.
Changelog:
[Internal]
Reviewed By: sammy-SC
Differential Revision: D41209331
fbshipit-source-id: 3ef9c3543b581a716a1e41e524957867ee811675