docs: fix doubled data field in notification examples (argoproj#25354)

Signed-off-by: aibazhang <zhang@sansan.com>
Co-authored-by: aibazhang <zhang@sansan.com>

Author: aibazhang

docs/operator-manual/notifications/examples.md

@@ -102,7 +102,6 @@ apiVersion: v1
 kind: ConfigMap
 metadata:
   name: argocd-notifications-cm
-data:
 data:
   service.slack: |
     token: <your-slack-bot-token>