[docs] document dim argument to tensor.size() (#58777)
Summary:
[docs] document dim argument to tensor.size()
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58777
Reviewed By: gchanan
Differential Revision: D28641109
Pulled By: zou3519
fbshipit-source-id: 5cb46bb8abe45ed299843af38515e5db89ad02a1
