Minor stylistic update on repositories list

I noticed there was a useless space on some repo names, so I removed it and added a full stop at the end of some repo descriptions. I suggest to revise the file /app/src/main/repo.json in order to have a unified stylistic design. For example, as I did, full stops at the end of every description, but also capitalisation on "repo", "android" and things like that. That said, thank you for your work!