docs: add whatsnew entry

Author: Alvaro-Kothe

doc/source/whatsnew/v2.3.4.rst

@@ -13,6 +13,7 @@ including other versions of pandas.
 Bug fixes
 ^^^^^^^^^
 - Bug in :meth:`DataFrame.__getitem__` returning modified columns when called with ``slice`` in Python 3.12 (:issue:`57500`)
+- Bug in :meth:`Series.str.replace` raising an error on valid group references (``\1``, ``\2``, etc.) on series converted to PyArrow backend dtype (:issue:`62653`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_234.contributors: