GUADALAJARA, Mexico—Garbiñe Muguruza’s trip to Mexico started last week with a taste of tequila. After winning the WTA Finals on Wednesday, it ended the same way. Muguruza defeated Anett Kontaveit 6–3, 7–5 in the final for her first title at the WTA’s elite, season-ending championships. She became the oldest champion at 28 since Serena Williams in 2014, and finishes the season at No. 3 in the rankings, her best performance since 2017, when she was No. 1. Before the tournament, Muguruza took a 37-mile (60-kilometer) ride to Tequila, a small town outside of Guadalajara where the popular spirit is produced. “I went to the town, did a tasting. I need to do this before because when I win …” Muguruza said. “We’re [now] going to have some tequila, have fun, lose all the tension we’ve been having and holding. I think the whole team deserves it.” Muguruza became the first …