GHA CI: make the default config use only one GPU (#68382)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/66511
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68382
Reviewed By: mrshenli
Differential Revision: D32441585
Pulled By: janeyx99
fbshipit-source-id: d92407c9bb9e4f740435840b4022e75749d7f0ba
