external-secrets: sync with server-side apply

Needed from ESO 0.19, whose CRDs are too big for client-side apply. Turned on now, on 0.10.7, so Argo CD migrates the managed fields before the upgrade starts.

apps/templates/external-secrets-helm.yaml

@@ -8,7 +8,9 @@ metadata:
 spec:
   syncPolicy:
     syncOptions:
-      - CreateNamespace=true 
+      - CreateNamespace=true
+      # From 0.19 the ESO CRDs are too big for client-side apply.
+      - ServerSideApply=true
     automated:
       selfHeal: true
   project: default