Unfortunately, the generated
curl commands in Jira documentation are entirely unreliable because they do not properly account for authentication.
I’m not sure exactly what you are trying to do with webhooks. Long ago, I created a simple webhook sample App (without ACE) just to explore all the underlying mechanics. That uses the “static” webhooks, registered at the time of installation. Will that work for your needs?
If what you need is dynamic, then your app can only manage the webhooks your app has created. So, to be clear, are you trying to delete a webhook registered by your app? Can you provide more information about the error you see when issuing a delete request?