revert STATE_DEREGISTERED check to see what will happen

tokio/src/runtime/time/entry.rs

@@ -170,13 +170,6 @@ impl StateCell {
         // with relaxed ordering.
         let mut cur_state = self.state.load(Ordering::Relaxed);
         loop {
-            // This entry is in the `guarded_list`, so it can not be removed
-            // from the entry list with the same `level` and `slot`.
-            // Because its state is STATE_DEREGISTERED, it has been fired.
-            if cur_state == STATE_DEREGISTERED {
-                break Err(cur_state);
-            }
-
             // improve the error message for things like
             // https://github.com/tokio-rs/tokio/issues/3675
             assert!(