Revert dask versioning of concat dispatch (rapidsai#7823)

Dependent on : dask/dask#7500

With the changes in above dask PR we would not have to version the concat dispatch in `dask-cudf`.

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

Approvers:
  - https://github.com/jakirkham

URL: rapidsai#7823

python/dask_cudf/dask_cudf/backends.py

@@ -1,13 +1,10 @@
 # Copyright (c) 2020-2021, NVIDIA CORPORATION.
 
-from distutils.version import LooseVersion
-
 import cupy as cp
 import numpy as np
 import pandas as pd
 import pyarrow as pa
 
-import dask
 from dask.dataframe.categorical import categorical_dtype_dispatch
 from dask.dataframe.core import get_parallel_type, make_meta, meta_nonempty
 from dask.dataframe.methods import (
@@ -31,7 +28,6 @@
 get_parallel_type.register(cudf.DataFrame, lambda _: DataFrame)
 get_parallel_type.register(cudf.Series, lambda _: Series)
 get_parallel_type.register(cudf.Index, lambda _: Index)
-DASK_VERSION = LooseVersion(dask.__version__)
 
 
 @meta_nonempty.register(cudf.Index)
@@ -205,45 +201,26 @@ def make_meta_object(x, index=None):
     raise TypeError(f"Don't know how to create metadata from {x}")
 
 
-if DASK_VERSION > "2021.03.1":
-
-    @concat_dispatch.register((cudf.DataFrame, cudf.Series, cudf.Index))
-    def concat_cudf(
-        dfs,
-        axis=0,
-        join="outer",
-        uniform=False,
-        filter_warning=True,
-        sort=None,
-        ignore_index=False,
-        **kwargs,
-    ):
-        assert join == "outer"
-
-        ignore_order = kwargs.get("ignore_order", False)
-        if ignore_order:
-            raise NotImplementedError(
-                "ignore_order parameter is not yet supported in dask-cudf"
-            )
-
-        return cudf.concat(dfs, axis=axis, ignore_index=ignore_index)
-
-
-else:
-
-    @concat_dispatch.register((cudf.DataFrame, cudf.Series, cudf.Index))
-    def concat_cudf(
-        dfs,
-        axis=0,
-        join="outer",
-        uniform=False,
-        filter_warning=True,
-        sort=None,
-        ignore_index=False,
-    ):
-        assert join == "outer"
+@concat_dispatch.register((cudf.DataFrame, cudf.Series, cudf.Index))
+def concat_cudf(
+    dfs,
+    axis=0,
+    join="outer",
+    uniform=False,
+    filter_warning=True,
+    sort=None,
+    ignore_index=False,
+    **kwargs,
+):
+    assert join == "outer"
+
+    ignore_order = kwargs.get("ignore_order", False)
+    if ignore_order:
+        raise NotImplementedError(
+            "ignore_order parameter is not yet supported in dask-cudf"
+        )
 
-        return cudf.concat(dfs, axis=axis, ignore_index=ignore_index)
+    return cudf.concat(dfs, axis=axis, ignore_index=ignore_index)
 
 
 @categorical_dtype_dispatch.register((cudf.DataFrame, cudf.Series, cudf.Index))