[DOC] Fix output of Shellwords.escape() by @anatol [Fixes GH-483]

* lib/shellwords.rb:  Fix output of Shellwords.escape()
https://github.com/ruby/ruby/pull/483
[ci-skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44211 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/shellwords.rb

@@ -33,7 +33,7 @@
 # This method will escape the String for you to safely use with a Bourne shell.
 #
 #   argv = Shellwords.escape("special's.txt")
-#   argv #=> "special\\s.txt"
+#   argv #=> "special\\'s.txt"
 #   system("cat " + argv)
 #
 # Shellwords also comes with a core extension for Array, Array#shelljoin.