By Joseph McBride Brock Purdy has the opportunity to silence all of his critics by winning theSuper Bowl on Sunday, according to San Francisco 49ers icon Dennis Brown. The young quarterback has already produced one of the most inspiring stories in NFL history, after becoming franchise starter for the Niners despite being ‘Mr. Irrelevant’ in 2022. Purdy started his rookie season as a third-string quarterback, but after both Trey Lance and Jimmy Garoppolo suffered season-ending injuries, head coach Kyle Shanahan had no choice but to give the kid a chance. And the rest as they say is history, as …