Learning to rank tests failing

[davidkyle]

Several learning to rank tests are failing with the error:

Arrays are not almost equal to 2 decimals

FAILED tests/ml/test_ml_model_pytest.py::TestMLModel::test_learning_to_rank[rank:ndcg-False]
FAILED tests/ml/test_ml_model_pytest.py::TestMLModel::test_learning_to_rank[rank:map-True]
FAILED tests/ml/test_ml_model_pytest.py::TestMLModel::test_learning_to_rank[rank:map-False]
FAILED tests/ml/test_ml_model_pytest.py::TestMLModel::test_learning_to_rank[rank:pairwise-True]
FAILED tests/ml/test_ml_model_pytest.py::TestMLModel::test_learning_to_rank[rank:pairwise-False]

The first failure reproduces on my system with this command

pytest tests/ml/test_ml_model_pytest.py::TestMLModel::test_learning_to_rank[rank:ndcg-False]

[davidkyle]

Closed by #685