[internal][deps] dependabot updates for Github Actions?

[AnnaKornfeldSimpson]

@claremacrae Thanks again for your insights on dependencies the other day! In a small attempt to do something helpful in return:

1. I noticed that you get deprecation warnings on your CodeQL runs for the API syntax in the CodeQL config file itself. As far as I can tell, the version upgrade here is a backend change and will not affect anything about what CodeQL tests get run.
2. GitHub supports dependabot checking for updates to GitHub Actions APIs automatically.

[claremacrae]

Superb - I didn't know either of these things. Thank you very much indeed @AnnaKornfeldSimpson.

I will get to these at some point, but if you were inclined to put in a PR or two for these, it would really help. No pressure though.