Added torch.bitwise_not docstr (#23397)
Summary:
Fixing https://github.com/pytorch/pytorch/issues/23311
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23397
Differential Revision: D16505107
Pulled By: pbelevich
fbshipit-source-id: 8d515fc27e253469393941c8da23d8e0510e64df
