Matthew Heineman has taken his camera to some of the most dangerous places on earth. For “City of Ghosts” from 2017 he filmed those brave souls who dared to decry the Islamic State’s terror tactics in Syria. Heineman’s latest is “Retrograde,” which started out as a chronicle of the final battalion of Green Berets stationed in Afghanistan but became a record of a rushed U.S. exit, followed by a surge of Afghan refugees desperate to escape the Taliban’s