The Voice didn’t turn its chair around for Gwen Stefani. Ariana Grande — and not Gwen — has been tapped to replace Nick Jonas, 28, as the fourth coach for season 21. “Nick came on when Gwen took a break, but she had her heart set on returning,” a source tells In Touch . “In fact, she was expecting it!” The “Let Me Reintroduce Myself” singer, 51, was a coach on seasons 7, 9, 12, 17 and 19. (Her team member Carter Rubin won Season 19.) She’s worried because Ariana, 27, “is so popular that the show may decide to stick with her, which means Gwen may never return,” adds the source. “It’s a little awkward with Blake [Shelton, 44, Gwen’s fiancé,] at the show right now, because the producers…
