add balance promotion shop promotion

app/models/shop_promotion.rb

@@ -1,7 +1,7 @@
 class ShopPromotion < ActiveRecord::Base
     has_paper_trail
     self.table_name = "shop_promotions"
-    has_and_belongs_to_many :depart_record, :foreign_key => :depart
+    belongs_to :depart_record, :foreign_key => :depart
 
     validates :begin_time,:end_time,:name,:total,:depart, presence: true
     validate :product_validation