add type annotations to torch.nn.modules.fold (#49479)
Summary:
closes gh-49478
Fixes https://github.com/pytorch/pytorch/issues/49478
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49479
Reviewed By: mruberry
Differential Revision: D25723838
Pulled By: walterddr
fbshipit-source-id: 45c4cbd6f147b6dc4a5f5419c17578c49c201022
