Update service_container/factories.rst

Author: OskarStark

service_container/factories.rst

@@ -108,7 +108,7 @@ the class name can be omitted from the factory declaration.
 Let's suppose the ``NewsletterManager`` class has a ``create()`` method that needs
 to be called to create the object and need a sender::
 
-    // src/Email\NewsletterManager.php
+    // src/Email/NewsletterManager.php
     namespace App\Email;
 
     // ...