fix a typo

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39000 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-02-01

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39001 b2dd03c8-39d4-4d8f-98ff-823fe69b080e