test_old_thread_select.rb: ignore short wait on Windows

* test/-ext-/old_thread_select/test_old_thread_select.rb
  (test_old_select_signal_safe): ignore short wait on Windows.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43154 b2dd03c8-39d4-4d8f-98ff-823fe69b080e