Update actions/setup-python action to v4

[renovate[bot]]

This PR contains the following updates:

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

---

Release Notes

actions/setup-python

### [`v4`](https://togithub.com/actions/setup-python/compare/v3...v4) [Compare Source](https://togithub.com/actions/setup-python/compare/v3...v4)

---

Configuration

📅 Schedule: Branch creation - "before 8am" (UTC), 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, click this checkbox.

---

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