XGB 2.0.0 was [released](https://github.com/dmlc/xgboost/releases/tag/v2.0.0) last week (Sept 12, 2023). This causes 19 tests to [fail](https://github.com/microsoft/hummingbird/actions/runs/6202924126/job/16842625679). Many errors are related to NDCG ("NDCG is now the default objective function.")
