Enable xenial-cuda11.1-cudnn8-py3.6-gcc7 in GHA (#60196)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/60196
Test Plan:
https://github.com/pytorch/pytorch/issues/60198: https://github.com/pytorch/pytorch/actions/runs/947796763
I should have used `ghstack` but I forgot; will do that in the future.
Reviewed By: walterddr
Differential Revision: D29231161
Pulled By: samestep
fbshipit-source-id: 8299a248ca9c1d36c3845d1c8a10ca9bf7101124
