[pyspark] Use quantile dmatrix. (#8284)

tests/python-gpu/test_gpu_spark/test_data.py

@@ -20,4 +20,6 @@ from test_spark.test_data import run_dmatrix_ctor
 
 @pytest.mark.skipif(**tm.no_cudf())
 def test_qdm_ctor() -> None:
-    run_dmatrix_ctor(True)
+    run_dmatrix_ctor(is_dqm=True, on_gpu=True)
+    with pytest.raises(AssertionError):
+        run_dmatrix_ctor(is_dqm=False, on_gpu=True)

tests/python-gpu/test_gpu_with_dask/test_gpu_with_dask.py

@@ -188,12 +188,9 @@ def run_gpu_hist(
 
     # See note on `ObjFunction::UpdateTreeLeaf`.
     update_leaf = dataset.name.endswith("-l1")
-    if update_leaf and len(history) == 2:
+    if update_leaf:
         assert history[0] + 1e-2 >= history[-1]
         return
-    if update_leaf and len(history) > 2:
-        assert history[0] >= history[-1]
-        return
     else:
         assert tm.non_increasing(history)