style: minor cleanup (#642)

* style: minor cleanup

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: henryiii

tests/test_histogram.py

@@ -1,24 +1,18 @@
 import functools
 import operator
+import pickle
 import sys
+from collections import OrderedDict
 from io import BytesIO
 
+import env
 import numpy as np
 import pytest
 from numpy.testing import assert_array_equal
 from pytest import approx
 
 import boost_histogram as bh
 
-try:
-    import cPickle as pickle
-except ImportError:
-    import pickle
-
-from collections import OrderedDict
-
-import env
-
 
 def test_init():
     bh.Histogram()