Document bool tensors for bitwise_not. (#23800)
Summary:
Requested by vadimkantorov at https://github.com/pytorch/pytorch/pull/23621#issuecomment-517945167
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23800
Differential Revision: D16651008
Pulled By: gchanan
fbshipit-source-id: 4ce21158bd5dd142edcd951e7ac941521b3d54af