fix Hash#slice code example [ci skip]

actionmailer/lib/action_mailer/base.rb

@@ -5,7 +5,7 @@
 require 'active_support/core_ext/module/anonymous'
 require 'action_mailer/log_subscriber'
 
-module ActionMailer # :nodoc:
+module ActionMailer # :notdoc:
   # = Action Mailer
   #
   # Action Mailer allows you to send email from your application using a mailer

activesupport/lib/active_support/core_ext/hash/slice.rb

@@ -3,7 +3,7 @@ class Hash
   # limiting an options hash to valid keys before passing to a method:
   #
   #   def search(criteria = {})
-  #     assert_valid_keys(:mass, :velocity, :time)
+  #     criteria.assert_valid_keys(:mass, :velocity, :time)
   #   end
   #
   #   search(options.slice(:mass, :velocity, :time))