For sending this request, you have to be authorized. See the API Authorization page for more details.
There is no dedicated request to update an existing webhook configuration.
However, you can do the following if you want to update your webhook configuration:
List the existing webhook configurations (List webhook configurations)
Make the desired adjustments to the AddWebhook Object
Create a new webhook configuration using the adjusted webhook object (Create webhook configuration)
Remove the previous webhook configuration (Remove webhook configuration)