DEVON, Pa.—Two time Olympic team gold medalist McLain Ward will defend his Leading Open Jumper Rider title at the Devon Horse Show and Country Fair, which runs May 23 to June 2.   Ward of Brewster, N.Y., has entered last year’s Devon Open Jumper Champion Antares F, the horse he rode in the 2012 London Olympic Games.   Ward also won last year’s $100,000 Wells Fargo Grand Prix of Devon on Antares F, a class he has won six times in the last 10 years