Janice Johnston has been promoted to executive producer of ABC’s newsmagazine 20/20.Johnston, who has been senior producer of the show, is only the fourth person to lead the show as EP since its launch in 1978 (with original hosts Harold Hayes and Robert Hughes quickly replaced by Hugh Downs).Johnston will report to David Sloan, senior executive producer of network primetime content, who oversees the news division’s primetime programming.In a memo to staff, ABC News President James Goldston