[PyTorch] Reapply D25546409: Use .sizes() isntead of .size() in cat_serial_kernel_impl (#49762)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49762
This was reverted because it landed in a stack together with
D25542799 (https://github.com/pytorch/pytorch/commit/9ce1df079f6ea90dd4b7f9aa12a1a78d51a8b204), which really was broken.
ghstack-source-id: 119326870
Test Plan: CI
Reviewed By: maratsubkhankulov
Differential Revision: D25685905
fbshipit-source-id: f4ec9e114993f988d4af380677331c72dfe41c44
