Upgrade GitHub Actions

[cclauss]

• https://github.com/actions/checkout/releases
• https://github.com/actions/setup-python/releases

The creation of these PRs can be automated via GitHub's Dependabot. https://docs.github.com/en/code-security/dependabot/working-with-dependabot/keeping-your-actions-up-to-date-with-dependabot