Martha Stewart revealed she warned John F. Kennedy Jr. about not using a co-pilot just days before his fatal 1999 plane crash. During Tuesday’s “The Real Housewives of New York City” Season 16 premiere, Stewart told her makeup artist and new cast member, Daisy Toye, about the eerie final conversation she had with Kennedy Jr., who died in the crash with his wife, Carolyn Bessette, and her sister, Lauren. He was piloting the plane. “I was with John-John the Monday before the Friday when they died. He called me,” Stewart explained. “I was running Martha Stewart Living Magazine. He called me and he said he’s in trouble.” Kennedy Jr., according…