Use unscoped when create stock items in migration

By the time the migration runs the default scope with deleted_at was
already defined so mocking acts_as_paranoid doesn't make any difference

related to spree#3805

core/db/migrate/20130213191427_create_default_stock.rb

@@ -5,17 +5,12 @@ def up
     location = Spree::StockLocation.new(name: 'default')
     location.save(validate: false)
 
-    Spree::StockItem.class_eval do
-      # Column name check here for #3805
-      unless column_names.include?("deleted_at")
-        def self.acts_as_paranoid; end
-      end
-    end
-
     Spree::Variant.all.each do |variant|
-      stock_item = location.stock_items.build(variant: variant)
+      stock_item = Spree::StockItem.unscoped.build(stock_location: location, variant: variant)
       stock_item.send(:count_on_hand=, variant.count_on_hand)
-      stock_item.save!
+      # Avoid running default_scope defined by acts_as_paranoid, related to #3805,
+      # validations would run a query with a delete_at column tha might not be present yet
+      stock_item.save! validate: false
     end
 
     remove_column :spree_variants, :count_on_hand