How do I delete an old (2018-ish) playground set of files?

[twosmallkittens]

I have an old playground, before the playground was connected to github, that I would like to delete. Attempting to delete a file, it tells me I need to fork, but fork is creating a copy of the files into a new workspace, and the original anonymous files still exist.

URL is of the form: playground.jsreport.net/w/anon/guid

Any ideas? Is it something the dev team has to do?