fix: remove wrong factory from configuration

Problem
-------

The RefundFactory is not a factory designed to be use in sylius
resources. As a side effect it generates invalid services and may fail.

Solution
--------

Removing the factory configuration. Since it generates wrong service
configuration, it's probably not used anywere.

src/Resources/config/app/config.yml

@@ -14,7 +14,6 @@ sylius_resource:
         sylius_refund.refund:
             classes:
                 model: Sylius\RefundPlugin\Entity\Refund
-                factory: Sylius\RefundPlugin\Factory\RefundFactory
         sylius_refund.refund_payment:
             classes:
                 model: Sylius\RefundPlugin\Entity\RefundPayment