Update service_container/factories.rst

Author: OskarStark

service_container/factories.rst

@@ -100,7 +100,7 @@ create its object:
     the configured class name may be used by compiler passes and therefore
     should be set to a sensible value.
 
-You can also use the ``factory`` option to create services from static methods
+When the static factory method is on the same class as the created instance, the class name can be omitted from the factory declaration.
 of the class itself.
 Let's suppose the ``NewsletterManager`` class has a ``create()`` method that needs
 to be called to create the object and need a send email address::