Fix Laravel version

Author: Alex Garrett-Smith

.github/workflows/run-tests.yml

@@ -17,7 +17,7 @@ jobs:
         laravel: [9.*]
         stability: [prefer-lowest, prefer-stable]
         include:
-          - laravel: 8.*
+          - laravel: 9.*
             testbench: ^6.23
 
     name: P${{ matrix.php }} - L${{ matrix.laravel }} - ${{ matrix.stability }} - ${{ matrix.os }}