DETROIT — Gov. Gretchen Whitmer called on Canadian authorities Thursday to resolve a dispute over COVID-19 vaccination mandates that have led truckers in Windsor to block traffic into Canada over the Ambassador Bridge. “My message is simple: reopen traffic on the bridge,” Whitmer said in a statement. More than a quarter of all trade between the United States and Canada happens over the Ambassador Bridge, particularly of automobiles and their components. Since Monday, a group of truckers known as the Freedom Convoy has prevented travel into Canada, forcing drivers to reroute to Blue Water Bridg…