Veteran TV actors (and real-life cousins) Robbie and Stephen Amell take a different approach to the superhero adventure in “Code 8, ” a dystopian science-fiction film set in a future where super-powered mutants are relatively common and yet treated as pariahs. Robbie Amell plays Conner, whose ability to manipulate electricity captures the attention of telekinetic crime boss Garrett (Stephen Amell). Directed by Jeff Chan from a script by Chris Pare, “Code 8” is more ambitious and adult than the Amells’ TV shows “Arrow” and “The Flash. ” It’s also a lot less fun. The ideas outpace the action in a movie that’s clearly been made with passion and intelligence, but without the kind of zip that this kind of story demands. Even a down-to-earth superhero picture occasionally needs to fly.