Return the skillet to medium-high heat and add the shallot. Cook, stirring, until tender, about 1 minute. Stir in the chicken broth, scraping up any browned bits, then add the apricots, olives, and harissa. Cook until the apricots soften and the broth is reduced by 2/3rds, about 5 minutes; season with salt and pepper. Pour any accumulated juices from the chicken into the sauce.