[numpy] `torch.log1p` : promote integer inputs to float (#48002)
Summary:
Reference https://github.com/pytorch/pytorch/issues/42515
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48002
Reviewed By: ngimel
Differential Revision: D25148911
Pulled By: mruberry
fbshipit-source-id: 902d0ddf699debd6edd1b3d55f5c73932ca45e83