Remove StockLocation from ReturnAuthorization

We have only one default location and don't need it associated to
anything.

app/controllers/spree/admin/return_authorizations_controller.rb

@@ -23,7 +23,7 @@ module Spree
 
       def permitted_resource_params
         params.require(:return_authorization).
-          permit(:amount, :reason, :stock_location_id)
+          permit(:amount, :reason)
       end
     end
   end