Remove backward ops for miopen convolution (#69987)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69987
Stack from [ghstack](https://github.com/ezyang/ghstack):
* __->__ #69987
Test Plan: Imported from OSS
Reviewed By: albanD
Differential Revision: D33170379
Pulled By: jbschlosser
fbshipit-source-id: 6bc274f1d457ec5bddc8b52c2f1c44eaae2ff0ed
