TYP: fix mypy on master (pandas-dev#40930)

Author: jbrockmendel

pandas/core/groupby/generic.py

@@ -177,9 +177,6 @@ def pinner(cls):
 class SeriesGroupBy(GroupBy[Series]):
     _apply_allowlist = base.series_apply_allowlist
 
-    # Defined as a cache_readonly in SelectionMixin
-    _obj_with_exclusions: Series
-
     def _iterate_slices(self) -> Iterable[Series]:
         yield self._selected_obj
 
@@ -930,9 +927,6 @@ def pct_change(self, periods=1, fill_method="pad", limit=None, freq=None):
 @pin_allowlisted_properties(DataFrame, base.dataframe_apply_allowlist)
 class DataFrameGroupBy(GroupBy[DataFrame]):
 
-    # Defined as a cache_readonly in SelectionMixin
-    _obj_with_exclusions: DataFrame
-
     _apply_allowlist = base.dataframe_apply_allowlist
 
     _agg_examples_doc = dedent(