Add audit event for deleting web hooks

What does this MR do and why?

Closes #458817 (closed)

This change introduces a new audit event for when a user deletes a system/group/project hook.

MR acceptance checklist

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Screenshots or screen recordings

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How to set up and validate locally

1. Add a system hook, group hook and project hook.
2. Delete all the hooks created in step (1).
3. Navigate to:
   • /admin/audit_logs - you should see the hooks deleted here along with their contexts.
   • In the group, navigate to Secure > Audit Events - you should see the deleted group hook.
   • In the prokect, navigate to Secure > Audit Events - you should see the deleted prokect hook.