Put whatsnew in I/O, fix msg

Author: ssikdar1

doc/source/whatsnew/v0.23.1.txt

@@ -45,7 +45,6 @@ Bug Fixes
 ~~~~~~~~~
 
 - tab completion on :class:`Index` in IPython no longer outputs deprecation warnings (:issue:`21125`)
-- fix normalize to not except when json_normalize is fed a key with null value on inner most key (:issue:`21158`)
 
 Groupby/Resample/Rolling
 ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -82,7 +81,7 @@ Indexing
 I/O
 ^^^
 
--
+- bug in :meth:`nested_to_record` when :meth:`json_normalize` was called with certain nested jsons  (:issue:`21158`)
 -
 
 Plotting