remove redundant IntervalIndexer.get_indexer_non_unique

Author: MarcoGorelli

pandas-stubs/core/indexes/interval.pyi

@@ -214,9 +214,6 @@ class IntervalIndex(ExtensionIndex[IntervalT, np.object_], IntervalMixin):
     @property
     def is_overlapping(self) -> bool: ...
     def get_loc(self, key: Label) -> int | slice | np_1darray_bool: ...
-    def get_indexer_non_unique(
-        self, target: Index
-    ) -> tuple[npt.NDArray[np.intp], npt.NDArray[np.intp]]: ...
     @property
     def left(self) -> Index: ...
     @property