test_io.rb: skip writev test

* test/ruby/test_io.rb (TestIO#test_puts_parallel): skip a test
  needs writev which is not portable.  [Feature #14042]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60424 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_io.rb

@@ -2446,6 +2446,7 @@ End
   end
 
   def test_puts_parallel
+    skip "not portable"
     pipe(proc do |w|
       threads = []
       100.times do