fix email regex example code [ci skip]

different from the regex in EmailValidator

activemodel/lib/active_model/validations/validates.rb

@@ -13,7 +13,7 @@ module ActiveModel
       #   validates :terms, acceptance: true
       #   validates :password, confirmation: true
       #   validates :username, exclusion: { in: %w(admin superuser) }
-      #   validates :email, format: { with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i, on: :create }
+      #   validates :email, format: { with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i, on: :create }
       #   validates :age, inclusion: { in: 0..9 }
       #   validates :first_name, length: { maximum: 30 }
       #   validates :age, numericality: true