Fix race in TestThread#test_thread_status_in_trap

* If the sleep is not enough to run the rest of the logic the process
  would be exited early, e.g., before the signal handler can run.

test/ruby/test_thread.rb

@@ -1068,7 +1068,7 @@ q.pop
         puts mth.status
         Process.kill(:INT, $$)
       }
-      sleep 0.1
+      sleep
     INPUT
   end