TOKYO—Poland scored an upset win in the inaugural Olympic 4×400 meters mixed relay on Saturday, with Dominican Republic picking up silver and the United States taking bronze. The Polish team, comprised of Karol Zalewski, Natalia Kaczmarek, Justyna Swiety-Ersetic, and Kajetan Duszynski, put on a gutsy performance inside the fan-free Olympic Stadium after posting the fastest time in Friday’s heats. It was the first Olympic medal for all four team mates, who cheered and embraced as anchor leg runner Duszynski crossed the finish line in a time of three minutes and 9.87 seconds. “I can’t believe it. It is a dream since childhood. It has come true,” Duszynski, 26, said after picking up Poland’s first gold medal of the Tokyo Games. The United States were the favorites after winning the event at the 2019 World Championships. But they almost did not make the final after they were disqualified for exchanging the …