Fix typing errors in the torch.distributions module (#45689)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/42979.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45689
Reviewed By: agolynski
Differential Revision: D24229870
Pulled By: xuzhao9
fbshipit-source-id: 5fc87cc428170139962ab65b71cacba494d46130
