update testbench in order to still support laravel 8 within tests

.github/workflows/main.yml

@@ -11,9 +11,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: ['8.0', '8.1', '8.2']
-        laravel: ['8.*', '11.*']
-        testbench: ['6.*', '9.*']
+        php: ["8.0", "8.1", "8.2"]
+        laravel: ["8.*", "11.*"]
+        testbench: ["6.*", "8.*"]
         dependency-version: [prefer-stable]
         include:
           - laravel: 8.*
@@ -22,9 +22,9 @@ jobs:
             testbench: 9.*
         exclude:
           - laravel: 11.*
-            php: '8.0'
+            php: "8.0"
           - laravel: 11.*
-            php: '8.1'
+            php: "8.1"
 
     name: P${{ matrix.php }} - L${{ matrix.laravel }} - ${{ matrix.dependency-version }} - ubuntu-latest