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/roundcube/Chart.lock

@@ -4,9 +4,9 @@ dependencies:
   version: 4.6.2
 - name: postgres-cluster
   repository: oci://harbor.alexlebens.net/helm-charts
-  version: 7.8.0
+  version: 7.9.1
 - name: volsync-target
   repository: oci://harbor.alexlebens.net/helm-charts
   version: 0.8.0
-digest: sha256:6885799edd2217270ad37df5fb6fdd7582504622f2df8f6a4cbe67bd9a9abc94
-generated: "2026-03-06T01:15:27.781474945Z"
+digest: sha256:5cfad7a46f5671378adac77c3e39df224430a7481aeb16f7d3713f134e5d1dab
+generated: "2026-03-11T23:02:03.844844518Z"