Fix precommit checks

Author: juleek

pandas/core/groupby/ops.py

@@ -1088,7 +1088,6 @@ def groups(self):
     def __iter__(self) -> Iterator[Hashable]:
         return iter(self.groupings[0].grouping_vector)
 
-
     @property
     def nkeys(self) -> int:
         # still matches len(self.groupings), but we can hard-code