NEW YORK -- Fox News Channel will not renew a contract with weekend host Rita Cosby, as the two sides couldn't come to an agreement on an extension, the network said. Cosby hosted "The Big Story Weekend Edition With Rita Cosby" at 9 p.m. Saturday. On Sunday at 6 p.m. she hosted "Fox News Live With Rita Cosby." Cosby will leave the network immediately. No replacement host has been appointed, nor has a decision been made on the future of the shows, Fox News said. The 'Big Story' host's departure is immediate