Delete backwards compatibility Backend overload for registerOp (#25914)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25914
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Differential Revision: D17284083
Pulled By: ezyang
fbshipit-source-id: 430ac7ea2bd042b1f4bb874e53679d0fde326dec
