We have a couple casting shifts for Supergirl‘s fourth season, ahead of Monday’s finale. One fan-favorite character has been promoted, while we’ll be seeing less of an original character. First up, The CW has announced (via TV Line) that Jesse Rath’s Brainiac-5 will be a series regular next season. “Brainy” is a member of the Legion of Superheroes, alongside Mon-El and Imra. He has been an ally to Kara and the team, and he will return again in the finale. Executive producers Robert Rovner and Jessica Queller had this to say about Brainy’s promotion.  “We love the character of Brainiac-5 and can’t imagine anyone but Jesse Rath in the role. He…