Photo: Black Bear/Everett Collection Premiering at the Toronto International Film Festival in September, the boxing biopic Christy seemed like a sure-thing heavyweight contender: the kind of A-list indie passion project that typically makes cinematic splashdown during the Labor Day Venice-Telluride-Toronto festival corridor and sucks up more than its share of awards-season oxygen through the Oscars. Calibrated around a transformative performance by star-producer Sydney Sweeney — who dims her