Revert "Update testbench version for Laravel 12 in CI workflow"

This reverts commit 45fdab9.

Author: hapidjus

.github/workflows/run-tests.yml

@@ -26,7 +26,7 @@ jobs:
         stability: [prefer-lowest, prefer-stable]
         include:
           - laravel: 12.*
-            testbench: 11.*
+            testbench: 10.*
           - laravel: 11.*
             testbench: 9.*