webhooks: stale hook was not cleaned up

**Description**
We have identified a potential issue with the management of webhooks for a repository. Upon investigation on Zenodo, we discovered that the repository currently has two active webhooks directed to Zenodo: one created in 2018 and another in 2024.

**Problem**
Whenever a new release is received, it consistently utilizes the older webhook, which has invalid credentials. Consequently, the releases fail consistently due to this mismatch.

We

**Objective**
We aim to investigate whether this occurrence is consistent or if it was a one-time incident.

**Steps to Reproduce**

1. Have a repository jointly owned by two users (user A and user B).
2. Enable the repository with user A on Zenodo.
3. Verify the webhook created on Github.
4. Disable the repository.
5. Enable the repository with user B on Zenodo.
6. Verify the webhook created on Github.

**Expected Outcome**
If there are indeed two webhooks present in the repository, it indicates an issue with the cleanup process of webhooks.