++ fix postgresql namespace duplicate

infrastructure/postgresql/base/namespace.yaml

@@ -2,3 +2,5 @@ apiVersion: v1
 kind: Namespace
 metadata:
   name: postgresql
+  labels:
+    istio-injection: enabled

infrastructure/s3-proxy/base/kustomization.yaml

@@ -2,5 +2,4 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 namespace: postgresql
 resources:
-  - namespace.yaml
   - helmrelease.yaml