The former Nickelodeon stars performed songs from the beloved series. “No new friends,” Drake once famously said, and it looks like these three besties took it to heart. International popstar Ariana Grande performed in Atlanta on Tuesday, after cancelling a show in Lexington, Kentucky due to severe illness, and she was joined by two very special guests. The surprise performers were none other than Ari’s former Victorious costars, Liz Gillies …