DEP: upgrade Github Action dependencies

[neutrinoceros]

Apply all non-major upgrades available now.

[neutrinoceros]

I intentionally didn't upgrade codecov-action yet, because the latest version is a major (7.0.0) and the version notes doesn't contain any useful context, so I didn't want to just run with it, but seeing the state of CI, maybe older versions are just non-functional now ?

[Cadair]

It looks like they just backported 7.0 to 6.0.2 so might as well bump it: https://github.com/codecov/codecov-action/releases

[Cadair]

Looks like either 6.0.2 or 7.0 should fix it: codecov/codecov-action#1956

[Cadair]

This is going to break all users, so I'm going to do this one manually and release one last release in the 2.x series.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.66%. Comparing base (a7a7c50) to head (875b493).
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #398   +/-   ##
=======================================
  Coverage   66.66%   66.66%           
=======================================
  Files           2        2           
  Lines           6        6           
=======================================
  Hits            4        4           
  Misses          2        2           

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[Cadair]

Thanks @neutrinoceros