remove duplicated whatsnew

Author: jorisvandenbossche

doc/source/whatsnew/v2.3.0.rst

@@ -64,16 +64,6 @@ API changes
   empty :class:`Index` with ``object`` dtype when determining the dtype of the resulting
   Index (:issue:`60797`)
 
-.. _whatsnew_230.api_changes:
-
-API changes
-~~~~~~~~~~~
-
-- When enabling the ``future.infer_string`` option: Index set operations (like
-  union or intersection) will now ignore the dtype of an empty ``RangeIndex`` or
-  empty ``Index`` with object dtype when determining the dtype of the resulting
-  Index (:issue:`60797`)
-
 .. ---------------------------------------------------------------------------
 .. _whatsnew_230.deprecations: