update changelog with removed method note

CHANGELOG.md

@@ -12,7 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 - Endpoint `/orders/{order_id}/statuses` supporting `GET` for retrieving statuses. The entity returned by this conforms
   to the change proposed in [stapi-spec#239](https://github.com/stapi-spec/stapi-spec/pull/239).
-- RootBackend has new methods `get_order_statuses` and `set_order_status`
+- RootBackend has new method `get_order_statuses`
 - `*args`/`**kwargs` support in RootRouter's `add_product` allows to configure underlyinging ProductRouter
 
 ### Changed
@@ -27,6 +27,7 @@ none
 
 - Endpoint `/orders/{order_id}/statuses` supporting `POST` for updating current status was added and then
   removed prior to release
+- RootBackend method `set_order_status` was added and then removed
 
 ### Fixed