fix(code): small fix on code block

Author: Guikingone

service_container/injection_types.rst

@@ -321,7 +321,7 @@ which allow the container to return the newly created service:
         // ...
         $container->register('app.newsletter_manager', NewsletterManager::class)
             ->addMethodCall('withMailer', [new Reference('mailer')], true);
-`
+
 .. note::
 
     This type of injection require that you add a ``@return static`` docblock in order