.circleci: Remove pynightly jobs
These jobs didn't really fulfill the intended purpose that they had once
had since the travis python versions were basically locked to 3.7.
Going to go ahead and remove these along with its docker jobs as well
since we don't actively need them anymore.
Signed-off-by: Eli Uriegas <eliuriegas@fb.com>
ghstack-source-id: cdfc4fc2ae15a0c86d322cc706d383d6bc189fbc
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41134
