Switch to new enum syntax in example code [ci-skip]

activerecord/lib/active_record/attribute_methods/before_type_cast.rb

@@ -56,7 +56,7 @@ def read_attribute_before_type_cast(attr_name)
       # serialization.
       #
       #   class Book < ActiveRecord::Base
-      #     enum status: { draft: 1, published: 2 }
+      #     enum :status, { draft: 1, published: 2 }
       #   end
       #
       #   book = Book.new(status: "published")

activesupport/lib/active_support/core_ext/object/with_options.rb

@@ -68,7 +68,7 @@ class Object
   # You can access these methods using the class name instead:
   #
   #   class Phone < ActiveRecord::Base
-  #     enum phone_number_type: { home: 0, office: 1, mobile: 2 }
+  #     enum :phone_number_type, { home: 0, office: 1, mobile: 2 }
   #
   #     with_options presence: true do
   #       validates :phone_number_type, inclusion: { in: Phone.phone_number_types.keys }