Use python3 instead of /usr/bin/env python3 on Windows (#101437)
I'm seeing some curious flaky failure on Windows where python3 couldn't be found in the env, for example https://github.com/pytorch/pytorch/actions/runs/4983028765/jobs/8920011406 or https://github.com/pytorch/pytorch/actions/runs/4967229128/jobs/8889106289. On the other hand, other scripts invoked directly with python3 works fine in the same workflow.
So let's use use `python3 .github/scripts/parse_ref.py` instead. The binary python3 is in GITHUB_PATH populated by `setup-windows` step
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101437
Approved by: https://github.com/PaliC