One might think watching a play about cancer would be a depressing way to spend an evening. But Lake City Playhouse’s production of “Wit,” by Margaret Edson, defies those expectations in a deft and witty way. “Wit” is essentially a series of monologues, peppered by short scenes, delivered by Vivian Bearing, a professor of 17th century poetry who has two hours to live. She is a scholar of the poet John Donne, whose works and themes are woven throughout the script. Bearing is not given to chuckle, chortle or guffaw, but she has a biting wit that adds much to the story.