one_hot docs missing (#17142)
Summary:
one_hot docs is missing [here](https://pytorch.org/docs/master/nn.html#one-hot).
I dug around and could not find a way to get this working properly.
Differential Revision: D14104414
Pulled By: zou3519
fbshipit-source-id: 3f45c8a0878409d218da167f13b253772f5cc963
