LONDON  – Comcast (CMCSA.O) and Twenty-First Century Fox (FOXA.O) face a quick-fire auction for British broadcaster Sky (SKYB.L) on Saturday after neither side backed down in a drawn-out $34 billion battle. A deadline for U.S. cable giant Comcast and Rupert Murdoch’s Fox to declare that their all-cash offers for Sky would not be increased passed […]