Update actions/checkout action to v4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v3 -> v4

---

Release Notes

actions/checkout (actions/checkout)

### [`v4`](https://togithub.com/actions/checkout/blob/HEAD/CHANGELOG.md#v400) [Compare Source](https://togithub.com/actions/checkout/compare/v3...v4) - [Support fetching without the --progress option](https://togithub.com/actions/checkout/pull/1067) - [Update to node20](https://togithub.com/actions/checkout/pull/1436)

---

Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• [ ] If you want to rebase/retry this PR, check this box

---

This PR has been generated by Mend Renovate. View repository job log here.

[codecov[bot]]

Codecov Report

Merging #50 (c20ad9f) into main (f4be929) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #50   +/-   ##
=======================================
  Coverage   98.71%   98.71%           
=======================================
  Files           3        3           
  Lines         312      312           
=======================================
  Hits          308      308           
  Misses          4        4