misc: Keep GitHub Actions up to date with GitHub's Dependabot

[cclauss]

https://docs.github.com/en/code-security/dependabot/working-with-dependabot/keeping-your-actions-up-to-date-with-dependabot

Summary of changes

Closes

Pull Request Checklist

• Changes have tests
• Authors have been added to AUTHORS.md
• News fragment added in changelog.d. See CONTRIBUTING.md for details

[pganssle]

This seems likely to be noisy.

[cclauss]

Not as noisy as the 37 supply chain security warnings at the bottom right of
https://github.com/dateutil/dateutil/actions/runs/9164291629

GitHub Actions have very infrequent major version changes. setup-python, the most frequent, has only had four major upgrades in its lifetime. Also, when they are upgraded, it often happens in batches. The pattern: * will consolidate all GHA updates into a single pull request to further reduce chattiness. See: rapidfuzz/RapidFuzz#362

There is a tradeoff between supply chain security and chattiness. This repo has few GHAs that are updated rarely and usually in batches and we are using pattern: * to ensure that there will only ever be a single GHA upgrade PR at a time.