correct testbench version

Author: sinnbeck

.github/workflows/run-tests.yml

@@ -24,7 +24,7 @@ jobs:
           - laravel: 9.*
           - testbench: 7.*
           - laravel: 10.*
-            testbench: 9.*
+            testbench: 8.*
           - laravel: 11.*
             testbench: 9.*
           - laravel: 12.*