Preheat oven to 375. Prepare a 2-quart casserole dish with cooking spray; set aside. In a large saucepan, cook celery and onions until tender. Stir in soup, milk, black pepper, vegetables, and turkey. Mix well. Bring to a boil. Spoon hot mixture into prepared dish. Separate biscuit dough into five biscuits. Cut each biscuit into quarters. Arrange biscuit pieces over top turkey mixture in dish. Bake for 20 minutes, or until biscuits are golden brown and filling is bubbly.