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

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

kubernetes/apps/system-upgrade/system-upgrade-controller/ks.yaml

@@ -4,8 +4,6 @@ kind: Kustomization
 metadata:
   name: cluster-apps-system-upgrade-controller
   namespace: flux-system
-  labels:
-    substitution.flux.home.arpa/enabled: "true"
 spec:
   path: ./kubernetes/apps/system-upgrade/system-upgrade-controller/app
   prune: true
@@ -22,8 +20,6 @@ kind: Kustomization
 metadata:
   name: cluster-apps-system-upgrade-controller-plans
   namespace: flux-system
-  labels:
-    substitution.flux.home.arpa/enabled: "true"
 spec:
   dependsOn:
     - name: cluster-apps-system-upgrade-controller