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` |

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

clusters/cl01tl/helm/grafana-operator/Chart.lock

@@ -4,12 +4,12 @@ dependencies:
   version: 5.22.0
 - name: postgres-cluster
   repository: oci://harbor.alexlebens.net/helm-charts
-  version: 7.8.0
+  version: 7.9.1
 - name: valkey
   repository: oci://harbor.alexlebens.net/helm-charts
   version: 0.4.0
 - name: valkey
   repository: oci://harbor.alexlebens.net/helm-charts
   version: 0.4.0
-digest: sha256:6f4dc1456854cad04f387cef6e0a9c846e76eb811bf97f2b7b13877cb3f577bd
-generated: "2026-03-09T23:07:06.293890171Z"
+digest: sha256:45cdb638fe815c3fc9703626b902d0f69ed8ffd0625e0f95bd7b33682126433b
+generated: "2026-03-11T22:57:43.133815464Z"