feat: switch substitution.flux.home.arpa label to be enabled by default

Signed-off-by: Devin Buhl <devin@buhl.casa>

kubernetes/apps/default/echo-server/ks.yaml

@@ -4,8 +4,6 @@ kind: Kustomization
 metadata:
   name: cluster-apps-echo-server
   namespace: flux-system
-  labels:
-    substitution.flux.home.arpa/enabled: "true"
 spec:
   path: ./kubernetes/apps/default/echo-server/app
   prune: true