Remove defunkt allow_backord_shipping config
Remove defunkt allow_backord_shipping config

https://github.com/spree/spree/commit/bce76f40c40d3ae20e97cdb745fd5ce967b9176e

Fixes #6380

azclick/spree,azclick/spree,keatonrow/spree,keatonrow/spree,keatonrow/spree,azclick/spree,azclick/spree,keatonrow/spree