CI is always converting all episodes

Add some code, so CI only converts one episode from opus to mp3 (for the legacy apple feed). Right now it's doing that with every episode (as it should on the server, but there it skips the ones already converted). So CI runs take longer with each episode we put out.

EDIT: in other words: it should do this differently in CI vs. on the real server. in CI, only convert one episode.