Chore: Update readme requiring PostgreSQL v15 instead of v13

docs/deployment-guide/goals/production/README.md

@@ -29,7 +29,7 @@ To deploy an EDC multiple deployment units must be deployed and configured.
 |-------------------------------------------------------------------|---------------------------------------------------------------------------------------------|
 | An Auth Proxy / Auth solution of your choice.                     | (deployment specific, required to secure UI and management API)                             |
 | Reverse Proxy that merges multiple services and removes the ports | (deployment specific)                                                                       |
-| Postgresql                                                        | 13 or compatible version, one for the EDC-data one for the LH-data                          |
+| Postgresql                                                        | 15 or compatible version, one for the EDC-data one for the LH-data                          |
 | EDC Backend                                                       | edc-ce or edc-ce-mds, see [CHANGELOG.md](../../../../CHANGELOG.md) for compatible versions. |
 | EDC UI                                                            | edc-ui, see  [CHANGELOG.md](../../../../CHANGELOG.md) for compatible versions.              |