Fix missing permissions in all GitHub Actions workflows

[eflumerf]

Fixes https://github.com/Mu2e/mu2e-spack/security/code-scanning/7 and extends the fix to all workflows in the repository.

Add an explicit permissions block at the workflow root so all jobs inherit least-privilege defaults unless overridden. The safest minimal non-breaking baseline is:

• contents: read

This documents intended access and avoids inheriting broader defaults.

Changes applied to all four workflows in .github/workflows/:

• mu2e-format-single-pkg.yml
• git-whitespace.yml
• track_new_issues.yml
• track_new_prs.yml

No imports, methods, or dependencies are required (YAML config only).

Suggested fixes powered by Copilot Autofix. Review carefully before merging.

[eflumerf]

@copilot check all workflows for permission issue

[Copilot]

@copilot check all workflows for permission issue

Done — added permissions: contents: read to all three remaining workflows (git-whitespace.yml, track_new_issues.yml, track_new_prs.yml) in commit Add permissions: contents: read to all remaining workflow files. All four workflows in the repo now have explicit least-privilege permission blocks.