Remove usage of legacy autograd function (#22925)
Summary:
We are planning to put up a deprecation warning for legacy autograd function in 1.2: https://github.com/pytorch/pytorch/pull/22922. This PR removes all usage of legacy function in PyTorch core and test suite, to prepare for the eventual removal of legacy function.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22925
Differential Revision: D16344834
Pulled By: yf225
fbshipit-source-id: 8bf4cca740398835a08b7a290f3058c3e46781ba
