Enable multinomial for torch.half (#29266)
Summary:
Changelog:
- Re-enable multinomial sampling when the probability tensor has `dtype == torch.half`.
It seems to have been missed in https://github.com/pytorch/pytorch/issues/28481.
Fixes https://github.com/pytorch/pytorch/issues/29211
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29266
Differential Revision: D18619105
Pulled By: ezyang
fbshipit-source-id: 1f87e5183e75de5c5e0ffde862fc72d040b32864
