ci: determine PHPUnit version based on Laravel version

Author: JaZo

Diff for: .github/workflows/tests.yml

@@ -32,15 +32,13 @@ jobs:
           - laravel: 11.*
             php: 8.1
         include:
-          - php: 7.4
+          - laravel: 8.*
             phpunit: ^9.5
-          - php: '8.0'
+          - laravel: 9.*
             phpunit: ^9.5
-          - php: 8.1
-            phpunit: ^10.5
-          - php: 8.2
+          - laravel: 10.*
             phpunit: ^10.5
-          - php: 8.3
+          - laravel: 11.*
             phpunit: ^10.5
 
     name: P${{ matrix.php }} - L${{ matrix.laravel }} - ${{ matrix.stability }}