DULUTH — Mason Shea and Mackenzie Myran repeated as winners of the William A. Irvin 5K on Friday, making runs at history to jump start a historic 50th Grandma’s Marathon weekend. Shea, a 24-year-old from River Falls, Wisconsin, became the first four-time men’s champion by crossing the finish line at Bayfront Festival Park in 14 minutes, 58 seconds. It marks his first repeat victory having won previously in odd years in 2021, 2023 and 2025. “I wa…