Updates linalg warning + docs (#45415)
Summary:
Changes the deprecation of norm to a docs deprecation, since PyTorch components still rely on norm and some behavior, like automatically flattening tensors, may need to be ported to torch.linalg.norm. The documentation is also updated to clarify that torch.norm and torch.linalg.norm are distinct.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45415
Reviewed By: ngimel
Differential Revision: D23958252
Pulled By: mruberry
fbshipit-source-id: fd54e807c59a2655453a6bcd9f4073cb2c12e8ac
