Remove ONNX BatchNorm(12) test and converter. (#37309)
Summary:
Pursuant to https://github.com/onnx/onnx/pull/2750 we must remove PyTorch ONNX exporter related changes to BatchNorm(12) that were introduced as part of https://github.com/pytorch/pytorch/pull/35567. This change is also needed to unblock ONNX [BUILD CI failures](https://circleci.com/gh/onnx/onnx/4629?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link) caused by PyTorch/Caffe2 tests.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37309
Reviewed By: hl475
Differential Revision: D21288914
Pulled By: houseroad
fbshipit-source-id: 15b076a2af55918dcd57f4e2fc77accd3d1510bd
