Update testbench version for Laravel 11 support

Author: athphane

.github/workflows/run-tests.yml

@@ -25,7 +25,7 @@ jobs:
             testbench: 10.*
             carbon: 3.*
           - laravel: 11.*
-            testbench: 9.*
+            testbench: ^9.16
             carbon: ^2.63
           - laravel: 10.*
             testbench: 8.*