update release notes

Author: jonathanho168

doc/source/whatsnew/v2.2.0.rst

@@ -697,7 +697,7 @@ Other
 - Bug in rendering ``inf`` values inside a a :class:`DataFrame` with the ``use_inf_as_na`` option enabled (:issue:`55483`)
 - Bug in rendering a :class:`Series` with a :class:`MultiIndex` when one of the index level's names is 0 not having that name displayed (:issue:`55415`)
 - Bug in the error message when assigning an empty dataframe to a column (:issue:`55956`)
--
+- Enhanced :func:`pandas.factorize` to support an additional parameter `original_factorization`, allowing users to apply an existing factorization scheme to new data. This feature is useful for maintaining consistent category codes across different datasets (:issue:`12509`).
 
 .. ***DO NOT USE THIS SECTION***