remove unnecessary mrb_get_args in fiber_switch

mrbgems/mruby-fiber/src/fiber.c

@@ -156,7 +156,6 @@ fiber_switch(mrb_state *mrb, mrb_value self, int len, const mrb_value *a, mrb_bo
   if (c->status == MRB_FIBER_TERMINATED) {
     mrb_raise(mrb, E_FIBER_ERROR, "resuming dead fiber");
   }
-  mrb_get_args(mrb, "*", &a, &len);
   mrb->c->status = resume ? MRB_FIBER_RESUMING : MRB_FIBER_TRANSFERRED;
   c->prev = resume ? mrb->c : (c->prev ? c->prev : mrb->root_c);
   if (c->status == MRB_FIBER_CREATED) {