I'd say leave it up. It's part of your history, something that shows that you put a lot of effort into something, even if you didn't perceive it as "successful

I'd say leave it up. It's part of your history, something that shows that you put a lot of effort into something, even if you didn't perceive it as "successful". You undoubtedly learned a significant amount during the project, and the repo stands as proof of that.