Can't see files from deleted app id's

I would like to delete the cloud data from appid 260. This is CSS beta that was latter removed and is no longer in the steam store page but I still can see it in the remote storage https://store.steampowered.com/account/remotestorageapp/?appid=260. When I try to fetch the files it results in an error. Is it possible to completely remove appid 260 from the remotestorage?