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

qwhelan · jreback · commit 982c169a286d · 2018-11-28T19:29:58.000-05:00
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
 
