Grey’s Anatomy’s big case-of-the-week Thursday involved a bull rider who’d been well and truly stomped. But Winston might have felt like he’d been kicked just as hard as the patient when he learned that estranged wife Maggie was contemplating taking a position at the Heart Center of Chicago. Was the stage set for Kelly McCreary’s exit? Read on… ‘THERE ARE NO WRONG ANSWERS HERE’ | As the Chandra Wilson-directed “Cowgirls Don’t Cry” began, Maggie and Winston were singing one another’s praises to a