Fix dependency injection PHP sample code

Author: jdecool

components/dependency_injection.rst

@@ -297,9 +297,9 @@ config files:
                 ->set('mailer.transport', 'sendmail')
             ;
 
-            $container->services()
-                ->set('mailer', 'Mailer')
-                    ->args(['%mailer.transport%'])
+            $services = $container->services();
+            $services->set('mailer', 'Mailer')
+                ->args(['%mailer.transport%'])
 
             $services->set('mailer', 'Mailer')
                 // the param() method was introduced in Symfony 5.2.