Deleting Gists from Organization account

I recently transformed a user account to an organization.

In the old user account I created some Gists: green-coding-berlin’s gists · GitHub

Since we cannot edit them anymore or create new ones for the organization we moved them all to a repository.

Now I want to remove the Gists, but this seems to be not possible somehow. All the toggles for deleting / editing are gone.

Does anyone have a clue on how to delete them?