One day after insisting he’d stick with Marc Bulger, St. Louis Rams coach Scott Linehan benched his banged-up quarterback. The winless Rams will go with backup Gus Frerotte on Sunday against the Arizona Cardinals, Linehan said Wednesday. Frerotte and Bulger, who has been ineffective while playing with two broken ribs, both got the news Tuesday from the coach and the switch was made public before…