WASHINGTON—Donovan Mitchell scored 28 points, Rudy Gobert had 20 points and 11 rebounds, and the Utah Jazz extended their winning streak to seven games with a 123–98 victory over the Washington Wizards on Saturday night. Hassan Whiteside added 18 points and 14 rebounds off the bench as the Jazz completed a perfect four-game East Coast trip. “I think we’re a better team now than when we left,” Jazz coach Quin Snyder said. “That’s hopefully what competition does for you.” Mitchell shot 4 for 9 from long distance, while Gobert and Whiteside combined to go 17 of 19 from the floor as Utah took control in the third quarter after trailing by a point at halftime. The Jazz entered Saturday three games back of Western Conference leaders Phoenix and Golden State. “I think tonight, the way we played on both ends and the mindset that we had was really like a …