Revert r35180; the fix break the test. see [ruby-dev:30653]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@35220 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/lbtest.rb

@@ -44,6 +44,6 @@ end
 
 lb.sync
 print "#{n-1}: cont\n"
-lb.join
+# lb.join # [ruby-dev:30653]
 
 print "exit.\n"