[Form] Fix alphabetical order of imports

Author: alexandre-daubois

components/form.rst

@@ -579,10 +579,10 @@ method:
 
     .. code-block:: php-standalone
 
-        use Symfony\Component\HttpFoundation\Request;
-        use Symfony\Component\HttpFoundation\RedirectResponse;
         use Symfony\Component\Form\Extension\Core\Type\DateType;
         use Symfony\Component\Form\Extension\Core\Type\TextType;
+        use Symfony\Component\HttpFoundation\RedirectResponse;
+        use Symfony\Component\HttpFoundation\Request;
 
         // ...