By Andrew Gould Colin Kaepernick left the door open for an NFL return by posting a workout video on Twitter. However, it’s highly unlikely a team will welcome him back. On Thursday, the 34-year-old shared a brief video with the caption, “Still Working.” ESPN’s Adam Schefter quoted the tweet with a report from a source that Kaepernick is “in the best shape of his life” and “wants to play.” Pro Football Talk’s Mike Florio threw cold water over that possibility. “Starting five years ago, the NFL wrongfully colluded against Colin Kaepernick,” Florio wrote. “Five years of collusion later, the NFL h…