refactor: utilize YAML anchor for namespace definition in kube-prometheus-stack Kustomization

kubernetes/apps/observability/kube-prometheus-stack/app.ks.yaml

@@ -4,9 +4,9 @@ apiVersion: kustomize.toolkit.fluxcd.io/v1
 kind: Kustomization
 metadata:
   name: &app kube-prometheus-stack
-  namespace: observability
+  namespace: &namespace observability
 spec:
-  targetNamespace: observability
+  targetNamespace: *namespace
   commonMetadata:
     labels:
       app.kubernetes.io/name: *app