ghost-en: drop dead ghost-en-smtp ignoreDifferences (3c)

Old out-of-band ghost-en-smtp secret deleted (kubectl); SMTP now sourced from
Infisical-backed ghost-en-smtp-infisical. Remove the now-obsolete /data
ignoreDifferences stanza from both app manifests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ghost-en/argocd-app.yaml

@@ -12,13 +12,6 @@ spec:
   destination:
     server: https://kubernetes.default.svc
     namespace: ghost-en
-  ignoreDifferences:
-    - group: ""
-      kind: Secret
-      name: ghost-en-smtp
-      namespace: ghost-en
-      jsonPointers:
-        - /data
   syncPolicy:
     automated:
       prune: true