CI: Xfail test_umap_outliers to mitigate flaky test failure. (rapidsai#7430)

Mitigates rapidsai#7412

Authors:
  - Simon Adorf (https://github.com/csadorf)

Approvers:
  - Jim Crist-Harif (https://github.com/jcrist)

URL: rapidsai#7430

Author: csadorf

python/cuml/tests/test_umap.py

@@ -927,6 +927,7 @@ def test_umap_small_fit_large_transform():
     assert trust >= 0.9
 
 
+@pytest.mark.xfail(reason="https://github.com/rapidsai/cuml/issues/7412")
 @pytest.mark.parametrize("n_neighbors", [5, 15])
 @pytest.mark.parametrize("n_components", [2, 5])
 def test_umap_outliers(n_neighbors, n_components):