TST: Bump checkout version and add Python 3.12

[pllim]

Description

This pull request is to fix #364

[github-actions]

Thank you for your contribution! 🌌 This checklist is meant to remind the package maintainers who will review this pull request of some common things to look for.

• Do the proposed changes actually accomplish desired goals?
• Do the proposed changes follow the STScI coding guidelines?
• Are tests added/updated as required? If so, do they follow the STScI testing guidelines?
• Are docs added/updated as required?
• Is rebase and/or squash necessary? If so, please provide the author with appropriate instructions.
• Did the CI pass? If no, are the failures related?
• Is a change log needed?
• Is a milestone set? Milestone must be set but we cannot check for it on Actions; do not let the green checkmark fool you.

[github-actions]

👋 Thank you for your draft pull request! Do you know that you can use [ci skip] or [skip ci] in your commit messages to skip running continuous integration tests until you are ready?

[pllim]

What? All green on first try? For once the stack isn't trying to send me to an early grave.