Add back Tensor.nonzero type annotation (#43053)
Summary:
Closes gh-42998
The issue is marked for 1.6.1, if there's anything I need to do for a backport please tell me what that is.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43053
Reviewed By: izdeby
Differential Revision: D23131708
Pulled By: malfet
fbshipit-source-id: 2744bacce6bdf6ae463c17411b672f09707e0887
