update StackedBytesArray: revert oindex and vindex

Author: andersy005

xarray/coding/strings.py

@@ -249,12 +249,6 @@ def shape(self) -> tuple[int, ...]:
     def __repr__(self):
         return f"{type(self).__name__}({self.array!r})"
 
-    def _vindex_get(self, key):
-        return _numpy_char_to_bytes(self.array.vindex[key])
-
-    def _oindex_get(self, key):
-        return _numpy_char_to_bytes(self.array.oindex[key])
-
     def __getitem__(self, key):
         # require slicing the last dimension completely
         key = type(key)(indexing.expanded_indexer(key.tuple, self.array.ndim))