Add missing empty line

Author: Neirda24

service_container/service_subscribers_locators.rst

@@ -146,6 +146,7 @@ Without autowire
 If you are not using autowire you need to require either ``Psr\Container\ContainerInterface`` or ``Symfony\Contracts\Service\ServiceProviderInterface`` as a ``__construct`` argument or as a method call like ``setContainer(Psr\Container\ContainerInterface $container)``.
 
 .. code-block:: diff
+
       $services->set('my_service', SomeClass::class)
     +   ->call('setContainer', [service(ContainerInterface::class)])
     +   ->tag('container.service_subscriber')