thread_sync.c: [DOC] fix typo

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63161 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

thread_sync.c

@@ -696,7 +696,7 @@ queue_closed_p(VALUE self)
 /*
  *  Document-class: ClosedQueueError
  *
- *  The exception class which will be raised when pushing into a close
+ *  The exception class which will be raised when pushing into a closed
  *  Queue.  See Queue#close and SizedQueue#close.
  */