Requiring pp is not required now [ci skip]

- Followup of https://bugs.ruby-lang.org/issues/14123

From: Prathamesh Sonpatki <csonpatki@gmail.com>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61310 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/pp.rb

@@ -5,9 +5,6 @@ require 'prettyprint'
 ##
 # A pretty-printer for Ruby objects.
 #
-# All examples assume you have loaded the PP class with:
-#   require 'pp'
-#
 ##
 # == What PP Does
 #
@@ -560,4 +557,3 @@ module Kernel
   end
   module_function :pp
 end
-