[Update transforms.py]Add `TanhTransform` (#19785)
Summary:
Resolves https://github.com/pytorch/pytorch/issues/33195
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19785
Differential Revision: D19642395
Pulled By: ezyang
fbshipit-source-id: 73c386fb89cd195201757b5fa47d6c01914a1f8f
