anchor xgboost to 1.6.2 to make tests pass (#726)

* anchor xgboost to 1.6.2 to make tests pass

* adding comment per review

Author: jperez999

docker/dockerfile.merlin

@@ -89,7 +89,8 @@ RUN pip install cupy-cuda117 nvidia-pyindex pybind11 pytest protobuf transformer
 RUN pip install betterproto cachetools graphviz nvtx scipy sklearn
 RUN pip install tritonclient[all] grpcio-channelz fiddle wandb
 RUN pip install git+https://github.com/rapidsai/asvdb.git@main
-RUN pip install xgboost lightgbm treelite==2.3.0 treelite_runtime==2.3.0
+# xgboost and treelite are pinned from tritonserver support
+RUN pip install xgboost==1.6.2 lightgbm treelite==2.3.0 treelite_runtime==2.3.0
 RUN pip install lightfm implicit
 RUN pip install numba
 RUN pip install "cuda-python>=11.5,<12.0"