[hot fix] Disable MPS tests as machines are down (#79119)
Trunk CI is suffering and not running these tests as the runner is unavailable. https://hud.pytorch.org/minihud?name_filter=trunk%20/%20macos-12.3-py3.8-arm64-test%20/%20Run%20MPS%20tests
https://github.com/pytorch/pytorch/runs/6789461040?check_suite_focus=true
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79119
Approved by: https://github.com/atalman
