“Saturday Night Live” cast members won’t be forced to appear alongside controversial billionaire Elon Musk when he hosts the show, Page Six is told. “Speaking historically, if a cast member has been that unhappy, they don’t have to do it,” a source told us. “[‘SNL’ boss Lorne Michaels] won’t ever make them do anything they don’t want to do.” The Tesla founder, 49, is set to helm the NBC institution on May 8 — but some cast members have made it clear that they’re less than enthused by the prospect of having him on stage at Studio 8H. After Musk...