Fix assert_eq import from cudf

[jrbourbeau]

gpuCI is failing with errors like this

13:20:30 ________________________ test_ping_pong_cudf[<lambda>8] ________________________
13:20:30 

13:20:30 ucx_loop = <_UnixSelectorEventLoop running=False closed=False debug=False>
13:20:30 g = <function <lambda> at 0x7f708ff1a660>
13:20:30 

13:20:30     @pytest.mark.parametrize(
13:20:30         "g",
13:20:30         [
13:20:30             lambda cudf: cudf.Series([1, 2, 3]),
13:20:30             lambda cudf: cudf.Series([], dtype=object),
13:20:30             lambda cudf: cudf.DataFrame([], dtype=object),
13:20:30             lambda cudf: cudf.DataFrame([1]).head(0),
13:20:30             lambda cudf: cudf.DataFrame([1.0]).head(0),
13:20:30             lambda cudf: cudf.DataFrame({"a": []}),
13:20:30             lambda cudf: cudf.DataFrame({"a": ["a"]}).head(0),
13:20:30             lambda cudf: cudf.DataFrame({"a": [1.0]}).head(0),
13:20:30             lambda cudf: cudf.DataFrame({"a": [1]}).head(0),
13:20:30             lambda cudf: cudf.DataFrame({"a": [1, 2, None], "b": [1.0, 2.0, None]}),
13:20:30             lambda cudf: cudf.DataFrame({"a": ["Check", "str"], "b": ["Sup", "port"]}),
13:20:30         ],
13:20:30     )
13:20:30     @gen_test()
13:20:30     async def test_ping_pong_cudf(ucx_loop, g):
13:20:30         # if this test appears after cupy an import error arises
13:20:30         # *** ImportError: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `CXXABI_1.3.11'
13:20:30         # not found (required by python3.7/site-packages/pyarrow/../../../libarrow.so.12)
13:20:30         cudf = pytest.importorskip("cudf")
13:20:30 >       from cudf.testing._utils import assert_eq
13:20:30 E       ImportError: cannot import name 'assert_eq' from 'cudf.testing._utils' (/opt/conda/envs/dask/lib/python3.11/site-packages/cudf/testing/_utils.py)
13:20:30 

13:20:30 distributed/comm/tests/test_ucx.py:201: ImportError

Based on rapidsai/cudf#16063 I think we should use from cudf.testing import assert_eq. Though I'm not really sure -- let's see if this helps CI.

cc @rjzamora @wence- @charlesbluca for visibility

[rjzamora]

Thanks @jrbourbeau !

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

    29 files  ±0      29 suites  ±0   11h 12m 49s ⏱️ - 3m 39s
 4 083 tests ±0   3 966 ✅ +4    112 💤 ±0  5 ❌  - 4 
55 230 runs  ±0  52 792 ✅ +4  2 432 💤 ±0  6 ❌  - 4 

For more details on these failures, see this check.

Results for commit 054d814. ± Comparison against base commit 9d36228.