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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### Configuration

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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/authentik/Chart.lock

@@ -7,9 +7,9 @@ dependencies:
   version: 2.4.0
 - 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
-digest: sha256:fad7059feb4ac80e06cd571a56215d56e4894eba69fb54aaa1e53ced9ec1b2b1
-generated: "2026-03-09T23:06:05.608952158Z"
+digest: sha256:abb34b7bb54393236e695453aa1940497cb4def3d3a56a45ca004a22f8e05648
+generated: "2026-03-11T22:55:49.936164674Z"