Perhaps more interesting as an example of the power of storytelling than as an in-depth historical examination, Errol Morris’ “My Psychedelic Love Story” — which closes out the AFI 2020 festival on its way to Showtime — marks another case of the documentarian finding a fascinating figure and then allowing that person to tell their own side of the story, leaving it to audiences to decide how much is truth and how much is self-aggrandizing rationalization.