Three-time Grammy Award-winning singer-songwriter Kirstin Maldonado, a member of Pentatonix, will join the Broadway cast of SIX beginning June 1. Maldonado will play Anne Boleyn. Dylan Mulvaney will play her final performance as Anne Boleyn on May 31. SIX, by Tony Award-winners Toby Marlow and Lucy Moss, is currently playing an open-ended run at the Lena Horne Theatre. Kirstin Maldonado joins continuing Queens:…