Embed torch.nn typing annotations (#43044)
Summary:
Delete several .pyi files and embed annotations from those files in respective .py
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43044
Reviewed By: ezyang
Differential Revision: D23123234
Pulled By: malfet
fbshipit-source-id: 4ba361cc84402352090523924b0035e100ba48b1
