REF: remove unnecessary maybe_cast_result (#38165)

Author: jbrockmendel

pandas/core/groupby/generic.py

@@ -35,7 +35,6 @@
 
 from pandas.core.dtypes.cast import (
     find_common_type,
-    maybe_cast_result,
     maybe_cast_result_dtype,
     maybe_downcast_numeric,
 )
@@ -1148,7 +1147,6 @@ def _aggregate_item_by_item(self, func, *args, **kwargs) -> DataFrame:
             data = obj[item]
             colg = SeriesGroupBy(data, selection=item, grouper=self.grouper)
 
-            cast = self._transform_should_cast(func)
             try:
                 result[item] = colg.aggregate(func, *args, **kwargs)
 
@@ -1161,10 +1159,6 @@ def _aggregate_item_by_item(self, func, *args, **kwargs) -> DataFrame:
                 cannot_agg.append(item)
                 continue
 
-            else:
-                if cast:
-                    result[item] = maybe_cast_result(result[item], data)
-
         result_columns = obj.columns
         if cannot_agg:
             result_columns = result_columns.drop(cannot_agg)