fix crash bug on Windows

mrbgems/mruby-io/test/mruby_io_test.c

@@ -75,8 +75,6 @@ mrb_io_test_io_setup(mrb_state *mrb, mrb_value self)
     mrb_raise(mrb, E_RUNTIME_ERROR, "can't create temporary file");
     return mrb_nil_value();
   }
-  close(fd0);
-  close(fd1);
 #if !defined(_WIN32) && !defined(_WIN64)
   fd2 = mkstemp(symlinkname);
   fd3 = mkstemp(socketname);