clarify the documentation of `torch.meshgrid` (#62977)
Summary:
Also warn about the behavior differences from `numpy.meshgrid`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62977
Reviewed By: mruberry, ngimel
Differential Revision: D30220930
Pulled By: dagitses
fbshipit-source-id: ae6587b41792721cae2135376c58121b4634e296
