chore(deps): update postgres-cluster docker tag to v7.9.1 (#4639)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [postgres-cluster](https://github.com/cloudnative-pg/cloudnative-pg) | minor | `7.8.0` → `7.9.1` |

---

### 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.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My41OS4yIiwidXBkYXRlZEluVmVyIjoiNDMuNTkuMiIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiY2hhcnQiLCJpbWFnZSJdfQ==-->

Reviewed-on: #4639
Co-authored-by: Renovate Bot <renovate-bot@alexlebens.net>
Co-committed-by: Renovate Bot <renovate-bot@alexlebens.net>

clusters/cl01tl/helm/argo-workflows/Chart.lock

@@ -7,6 +7,6 @@ dependencies:
   version: 2.4.20
 - name: postgres-cluster
   repository: oci://harbor.alexlebens.net/helm-charts
-  version: 7.8.0
-digest: sha256:772ba83a6e0fa6a7e3633ff1fff0f8221b45a1f36ec890489cfa383330d99f81
-generated: "2026-02-27T18:14:32.22595048Z"
+  version: 7.9.1
+digest: sha256:c3f9876ca432887c05eaa87d4e6006dcb8b3a5e654dc976103426a313fde12bc
+generated: "2026-03-11T22:55:29.202299472Z"