Whitney Leavitt is leaving “ The Secret Lives of Mormon Wives .” The reality star-turned-actress announced the news on Sunday in the middle of her final performance of “Chicago” on Broadway. She has been leading the revival as Roxie Hart since early February, and used a monologue in the show to nod at her “Mormon Wives” career ending. She later followed up with an Instagram video discussing the decision in more depth and clarifying that she will still appear throughout Season 5, which is currently in production. In a video posted by TMZ , Leavitt is seen onstage in character as Roxie while a man shows her a newspaper. The scene is about articles being written about Roxie, but at one point, she sees a headline and says, “What is that? Whitney Leavitt Announces She’s Leaving ‘The Secret Lives of Mormon Wives’?” The audience erupts in cheers and applause.…