Update actions/checkout to v4 to stop node deprecation warnings

[SavageCore]

Description

Update actions/checkout to v4 to stop node deprecation warnings
https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[JelleZijlstra]

Thanks! Could you retarget this PR to the main branch instead of the stable branch?

[cooperlees]

Thanks, but I wonder if we should look into why Dependabot missed this? Or did the PR get closed?

[SavageCore]

Thanks! Could you retarget this PR to the main branch instead of the stable branch?

Done, I just did it quickly from the edit button on the docs website, perhaps that target needs updating?

[cobaltt7]

Thanks, but I wonder if we should look into why Dependabot missed this? Or did the PR get closed?

This doesn't update the repo CI, which already uses v4. This updates the docs for using Black in Actions.

[cooperlees]

Ahh, my bad, Didn't look close enough ...

[JelleZijlstra]

perhaps that target needs updating

Not sure what you mean there. The stable branch gets updated on releases.

[SavageCore]

perhaps that target needs updating

Not sure what you mean there. The stable branch gets updated on releases.

I mean, if you want PRs coming in to target main then the edit link https://github.com/psf/black/edit/stable/docs/integrations/github_actions.md should change to https://github.com/psf/black/edit/main/docs/integrations/github_actions.md? Perhaps that isn't possible, I've not used Sphinx.

[JelleZijlstra]

I see, you mean the links on https://black.readthedocs.io/en/stable/ at the top. It wasn't clear from the previous messages in this PR that that's what you were doing. It would be good if we could edit that link to create PRs to the main branch instead, but I don't know how hard that is to do.

For this PR, you'll have to run prettier to reformat some of the markdown files you changed.

[SavageCore]

For this PR, you'll have to run prettier to reformat some of the markdown files you changed.

Done. prettier seems happy now!