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

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

Author: pre-commit-ci[bot]

tests/test_histogram_indexing.py

@@ -447,6 +447,7 @@ def test_scale_flowbins():
 
     assert scale_value == approx(ref_value)
 
+
 def test_scale_flowbins():
     h = bh.Histogram(bh.axis.Variable([0, 0.5, 1]), storage=bh.storage.Weight())