Update ghcr.io/geek-cookbook/gatus Docker tag to v5.9.0

[funkypenguin-autochef]

This PR contains the following updates:

Package	Update	Change
ghcr.io/geek-cookbook/gatus	minor	5.8.0 -> 5.9.0

---

⚠ Dependency Lookup Warnings ⚠

Warnings were logged while processing this repo. Please check the logs for more information.

---

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 is behind base branch, 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 Renovate Bot.