fix: match pg-cluster manifest to live CNPG cluster state

- Remove imageName (was never applied, live cluster uses default CNPG image)
- Remove maintenance_work_mem (live cluster has no custom parameters)
- Set postgresql: {} to match live state
- Keep memory role superuser: true (the only needed change)

Fixes CNPG admission webhook: 'Can't change image name and configuration at the same time'

apps/base/customer1/hermes-db/pg-cluster-hermes.yaml

@@ -6,15 +6,10 @@ metadata:
 
 spec:
   instances: 1
-  # Custom image with pgvector extension
-  imageName: "gcr.io/devops-lab-cluster/postgres-pgvector:15.2-0.8.0"
   storage:
     size: 20Gi
 
-  postgresql:
-    parameters:
-      # pgvector HNSW index memory settings
-      maintenance_work_mem: "256MB"
+  postgresql: {}
 
   managed:
     roles: