[BUG] Missing webhook-Case management connector API doc

[ghost]

Description:

Missing webhook-Case management connector API doc.

URL link or topic name:
https://www.elastic.co/guide/en/security/current/actions-api-overview.html

Screenshots:

[lcawl]

I have created elastic/kibana#139763 to remove these duplicated API details from the Security Guide and I have elastic/kibana#138583 up to add the Webhook Case Management connector details to the APIs in the Kibana Guide. When those projects are complete, I think this issue will be unnecessary.