Remove guaranteed n+1 in line item option value condition

If we don't use pluck, we can preload.

Author: mamhoff

promotions/app/models/solidus_promotions/conditions/line_item_option_value.rb

@@ -10,7 +10,7 @@ class LineItemOptionValue < Condition
 
       def line_item_eligible?(line_item, _options = {})
         pid = line_item.product.id
-        ovids = line_item.variant.option_values.pluck(:id)
+        ovids = line_item.variant.option_value_ids
 
         product_ids.include?(pid) && (value_ids(pid) & ovids).present?
       end