“Broker,” the unconventional family drama which appeared in competition at last month’s Cannes Film Festival, topped the box office in South Korea on Wednesday, its opening day. “Broker” grossed $1.10 million, enough to depose crime actioner “The Roundup” from the top spot that it had enjoyed for the past three weeks and which had made it the highest performing film this year. According to data from the Kobis tracking service operated by the Korean Film Council, “Broker” played on 1,590 screens