apps: list external-snapshotter's automated sync once

apps/templates/snapshot-controller-helm.yaml

@@ -30,10 +30,8 @@ spec:
     server: https://kubernetes.default.svc
     namespace: kube-system
   syncPolicy:
+    # Was listed twice, with and without prune; Argo CD kept the last one.
     automated:
       selfHeal: true
-      prune: true
     syncOptions:
     - CreateNamespace=true
-    automated:
-      selfHeal: true