Fix documentation referring to removed as_gpu_matrix method. (#11937)

This fixes outdated documentation that refers to the `as_gpu_matrix` method, which was removed.

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

URL: #11937

docs/cudf/source/user_guide/cupy-interop.ipynb

@@ -42,7 +42,7 @@
     "\n",
     "2. We can also use `DataFrame.values`.\n",
     "\n",
-    "3. We can also convert via the [CUDA array interface](https://numba.pydata.org/numba-doc/dev/cuda/cuda_array_interface.html) by using cuDF's `as_gpu_matrix` and CuPy's `asarray` functionality."
+    "3. We can also convert via the [CUDA array interface](https://numba.pydata.org/numba-doc/dev/cuda/cuda_array_interface.html) by using cuDF's `to_cupy` functionality."
    ]
   },
   {

python/cudf/cudf/tests/test_dataframe.py

@@ -4286,26 +4286,26 @@ def test_series_values_property(data):
         pytest.param(
             {"A": [1, None, 3], "B": [1, 2, None]},
             marks=pytest.mark.xfail(
-                reason="Nulls not supported by as_gpu_matrix"
+                reason="Nulls not supported by values accessor"
             ),
         ),
         pytest.param(
             {"A": [None, None, None], "B": [None, None, None]},
             marks=pytest.mark.xfail(
-                reason="Nulls not supported by as_gpu_matrix"
+                reason="Nulls not supported by values accessor"
             ),
         ),
         {"A": [], "B": []},
         pytest.param(
             {"A": [1, 2, 3], "B": ["a", "b", "c"]},
             marks=pytest.mark.xfail(
-                reason="str or categorical not supported by as_gpu_matrix"
+                reason="str or categorical not supported by values accessor"
             ),
         ),
         pytest.param(
             {"A": pd.Categorical(["a", "b", "c"]), "B": ["d", "e", "f"]},
             marks=pytest.mark.xfail(
-                reason="str or categorical not supported by as_gpu_matrix"
+                reason="str or categorical not supported by values accessor"
             ),
         ),
     ],