Remove unreachable order recovery code

Every page load creates a cart order if none is present. So when a user
logs in, they always have an order stored in their session. And
therefore, we never got to recover an old order.

We could have fixed the code to restore old orders. But as far as I can
tell, order recovery hasn't been working for years and I couldn't find
any issue requesting this feature.

If we wanted to implement order recovery, it should probably be designed
more carefully and included in the `current_order` method.

lib/spree/core/controller_helpers/order.rb

@@ -68,18 +68,9 @@ module Spree
           session[:guest_token] = nil
         end
 
-        # Recover incomplete orders from other sessions after logging in.
+        # Load current order and create a new one if necessary.
         def set_current_order
-          return unless (user = spree_current_user)
-
-          last_incomplete_order = user.last_incomplete_spree_order
-
-          if session[:order_id].nil? && last_incomplete_order
-            session[:order_id] = last_incomplete_order.id
-          end
-
-          # Load current order and create a new one if necessary.
-          current_order(true)
+          current_order(true) if spree_current_user
         end
 
         def current_currency