Some Apps are in meta files (releases.json, dates.json, readmes.json and colors.json) but missing in `apps` directory

I tried to create an API which fetches app list from meta files and then get's the app's info by fetching the `.yml` file from `https://raw.githubusercontent.com/electron/apps/master/apps/${app}/${app}.yml`. But I got many 404 errors in the API. When I tested some of them manually, I saw that many apps are in meta files but not in the `apps` directory. I found no Pull Request for removal of those apps (for example, `ffftp`).