Move rubocop exception to rubocop todo

.rubocop_todo.yml

@@ -363,6 +363,13 @@ Rails/UniqueValidationWithoutIndex:
     - 'app/models/customer.rb'
     - 'app/models/exchange.rb'
 
+# Offense count: 2
+# Configuration parameters: Include.
+# Include: app/models/**/*.rb
+Rails/UniqueValidationWithoutIndex:
+  Exclude:
+    - 'app/models/spree/stock_item.rb'
+
 # Offense count: 1
 # Configuration parameters: Environments.
 # Environments: development, test, production

app/models/spree/stock_item.rb

@@ -7,9 +7,7 @@ module Spree
     has_many :stock_movements, dependent: :destroy
 
     validates :stock_location, :variant, presence: true
-    # rubocop:disable Rails/UniqueValidationWithoutIndex
     validates :variant_id, uniqueness: { scope: :stock_location_id }
-    # rubocop:enable Rails/UniqueValidationWithoutIndex
     validates :count_on_hand, numericality: { greater_than_or_equal_to: 0, unless: :backorderable? }
 
     attr_accessible :count_on_hand, :variant, :stock_location, :backorderable, :variant_id