message: silence lint
diff: @@ -116,7 +116,7 @@ fn recover_parallel_cycle() {
  #[test]
  fn panic_parallel_cycle() {
  - let mut db = ParDatabaseImpl::default();
  + let db = ParDatabaseImpl::default();
  db.knobs().signal_on_will_block.set(3);
  let thread_a = std::thread::spawn({
  