Skip another flaky Ractor test for YJIT

bootstraptest/test_ractor.rb

@@ -1543,7 +1543,7 @@ assert_equal "ok", %q{
 
   1_000.times { idle_worker, tmp_reporter = Ractor.select(*workers) }
   "ok"
-}
+} unless yjit_enabled # flaky with YJIT https://github.com/ruby/ruby/actions/runs/3575374374/jobs/6011846425
 
 assert_equal "ok", %q{
   def foo(*); ->{ super }; end