Extends warning on norm docs (#63310)

Extends warning on norm docs (#63310)

Summary:
torch.norm has a couple documentation issues, like https://github.com/pytorch/pytorch/issues/44552 and https://github.com/pytorch/pytorch/issues/38595, but since it's deprecated this PR simply clarifies that the documentation (and implementation) of torch.norm maybe be incorrect. This should be additional encouragement for users to migrate to torch.linalg.vector_norm and torch.linalg.matrix_norm.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/63310

Reviewed By: ngimel

Differential Revision: D30337997

Pulled By: mruberry

fbshipit-source-id: 0fdcc438f36e4ab29e21e0a64709e4f35a2467ba