Add documentation for torch.lgamma (#27812)
Summary:
Changelog:
- Add doc string in _torch_docs.py, _tensor_docs.py
- Expose in docs/source/torch.rst, docs/source/tensors.rst
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27812
Test Plan:
- Remove `lgamma`, `lgamma_` from the blacklist
Fixes https://github.com/pytorch/pytorch/issues/27783
Differential Revision: D17907630
Pulled By: ezyang
fbshipit-source-id: 14e662a4e5262126889a437e5c4bfb21936730e8
