📝(kubernetes) update doc with our dev-backend helm chart

We removed the usage of bitnami charts and created our own dev-backend
helm chart. We need to update the kubernetes document accordingly.

docs/examples/helm/postgresql.values.yaml

@@ -1,7 +1,9 @@
-auth:
+postgres:
+  enabled: true
+  name: postgres
+  #serviceNameOverride: postgres
+  image: postgres:16-alpine
   username: dinum
   password: pass
-  database: impress
-tls:
-  enabled: true
-  autoGenerated: true
+  database: dinum
+  size: 1Gi