Make one_hot non-differentiable. (#19430)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19430
ghimport-source-id: 6787473873fdc21400138a4322e17fee8db62607
Differential Revision: D15003382
Pulled By: gchanan
fbshipit-source-id: e9244c7a5f0ad7cd2f79635944a8b37f910231c9
