Remove code related to spree promotions

app/models/spree/product.rb

@@ -40,7 +40,6 @@ module Spree
 
     has_many :classifications, dependent: :delete_all
     has_many :taxons, through: :classifications
-    has_and_belongs_to_many :promotion_rules, join_table: :spree_products_promotion_rules
 
     belongs_to :tax_category, class_name: 'Spree::TaxCategory'
     belongs_to :shipping_category, class_name: 'Spree::ShippingCategory'
@@ -314,11 +313,6 @@ module Spree
       end
     end
 
-    def possible_promotions
-      promotion_ids = promotion_rules.map(&:activator_id).uniq
-      Spree::Promotion.advertised.where(id: promotion_ids).reject(&:expired?)
-    end
-
     def total_on_hand
       stock_items.sum(&:count_on_hand)
     end