Update github actions to add Laravel 11 to the test matrix.

.github/workflows/phpunit.yml

@@ -36,10 +36,14 @@ jobs:
       matrix:
         os: [ubuntu-latest]
         php: ['8.0', '8.1', '8.2']
-        laravel: ['9.*', '10.*']
+        laravel: ['9.*', '10.*', '11.*']
         exclude:
           - php: '8.0'
             laravel: '10.*'
+          - php: '8.0'
+            laravel: '11.*'
+          - php: '8.1'
+            laravel: '11.*'
 
     name: tests - PHP ${{ matrix.php }} - L${{ matrix.laravel }} - ${{ matrix.os }}