Update alpine Docker tag to v3.18.4

This MR contains the following updates:

Package	Type	Update	Change
alpine	ironbank-docker	patch	3.18.3 -> 3.18.4
alpine		patch	3.18.3 -> 3.18.4
alpine	final	patch	3.18.3 -> 3.18.4
alpine	stage	patch	3.18.3 -> 3.18.4

---

Configuration

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

🚦 Automerge: Enabled.

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

🔕 Ignore: Close this MR and you won't be reminded about these updates again.

---

• If you want to rebase/retry this MR, check this box

---

This MR has been generated by Renovate Bot.