Fix prod wheel upload checkout auth fallback

[Copilot]

upload_prod / prod_whl_upload was failing during the pybatfish checkout step because the workflow supplied an empty explicit token instead of falling back to the default GitHub token. This change restores the intended auth behavior without reintroducing secret pass-through in the reusable workflow.

• Root cause

  • actions/checkout in prod_whl_upload used OPEN_SOURCE_BUILDKITEBOT_PUBLIC_REPO_TOKEN directly.
  • When that secret was absent, checkout failed with Input required and not supplied: token instead of using the default workflow token.

• Workflow auth behavior

  • Keep OPEN_SOURCE_BUILDKITEBOT_PUBLIC_REPO_TOKEN out of workflow_call secret plumbing.
  • Update the pybatfish checkout step to fall back to github.token:

token: ${{ secrets.OPEN_SOURCE_BUILDKITEBOT_PUBLIC_REPO_TOKEN || github.token }}

• Scope
  • Remove the secret pass-through added in cross_version_test.yml.
  • Remove the corresponding required secret declaration from reusable-upload.yml.
  • Limit the change to the prod_whl_upload checkout path.

[batfish-bot]

This change is 

[dhalperi]

@dhalperi reviewed 1 file and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on copilot[bot]).

[dhalperi]

@dhalperi reviewed 1 file and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on copilot[bot]).