Update alpine Docker tag to v3.20

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
alpine	final	minor	3.19 -> 3.20
alpine	stage	minor	3.19 -> 3.20

---

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 these updates again.

---

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

---

This PR was generated by Mend Renovate. View the repository job log.