CLN: remove unused import causing flake8 error on master (pandas-dev#23989)

qwhelan · Pingviinituutti · commit b23d35a3a8b1 · 2019-02-28T10:19:12.000+02:00
diff --git a/pandas/core/groupby/ops.py b/pandas/core/groupby/ops.py
@@ -7,7 +7,6 @@
 """
 
 import collections
-import copy
 
 import numpy as np
 
