The Academy of Motion Picture Arts and Sciences has narrowed the field for the Documentary Feature Oscar to 15 vying for five nomination slots. Among them are a sequel to a previous Oscar winner, a bracing look back at the 1992 Los Angeles riots and a topical look at Russia’s Olympic doping scandal. Here is the list: The 15 films are listed below in alphabetical order by title, with their production companies: Abacus: Small Enough to Jail Mitten Media, Motto Pictures…