dir.c: fix rdoc  [ci skip]

* dir.c (dir_s_aref): fix rdoc.  `Dir.glob` allows an array but
  `Dir[]` not.  the former accepts an optional parameter `flags`,
  while the latter accepts arbitrary number of arguments but no
  `flags`.  [ruby-core:65265] [Bug #10294]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47850 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-10-09

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47851 b2dd03c8-39d4-4d8f-98ff-823fe69b080e