Gwen Stefani showed support for her husband Blake Shelton while he wrapped up his 2023 ‘Back to the Honky Tonk’ tour. The “Hollaback Girl” singer-songwriter surprised the crowd at Shelton’s final concert in Buffalo, by performing No Doubt’s “Don’t Speak”, as well as two of her collaborations with the country star.   Stefani joined Shelton midway through his set during the…