Prim and proper Martha Stewart is publicly saying polite things about the Duchess of Sussex’s latest lifestyle company, American Riviera Orchard, but sources dished the domestic diva is no fan of Prince Harry’s wife, Meghan Markle, RadarOnline.com has learned. Stewart, 82, apparently can’t wait to celebrate the kitchen copycat’s downfall! Markle, 42, recently unveiled the new lifestyle brand and tipster tattle the former Suits actress plans to peddle crockery, serving ware, table linens and dog food to coincide with a cooking show. “Martha has seen hundreds of Meghan types come and go — and sa…