* common.mk: fixed broken reference of update-config_files task

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47740 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-09-30

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47741 b2dd03c8-39d4-4d8f-98ff-823fe69b080e