Update dask_cudf imports to be compatible with latest dask (#10442)

Updated imports to be compatible with latest dask after dask/dask#8796
This change is also compatible with dask versions prior to the above dask PR.

Tested `import dask_cudf` with both dask `2022.02.2a220314` and `2022.02.2a220315`.

Authors:
  - Rick Ratzel (https://github.com/rlratzel)

Approvers:
  - Ashwin Srinath (https://github.com/shwina)

URL: #10442

python/dask_cudf/dask_cudf/backends.py

@@ -6,6 +6,7 @@
 import numpy as np
 import pandas as pd
 import pyarrow as pa
+from pandas.api.types import is_scalar
 
 from dask.dataframe.core import get_parallel_type, meta_nonempty
 from dask.dataframe.dispatch import (
@@ -22,11 +23,10 @@
     UNKNOWN_CATEGORIES,
     _nonempty_scalar,
     _scalar_from_dtype,
-    is_arraylike,
-    is_scalar,
     make_meta_obj,
 )
 from dask.sizeof import sizeof as sizeof_dispatch
+from dask.utils import is_arraylike
 
 import cudf
 from cudf.api.types import is_string_dtype