pythongh-101578: mention in what's new in 3.12 that exceptions are now normalized before stored (python#102702)

Author: iritkatriel

Doc/whatsnew/3.12.rst

@@ -985,6 +985,11 @@ Porting to Python 3.12
   effects, these side effects are no longer duplicated.
   (Contributed by Victor Stinner in :gh:`98724`.)
 
+* The interpreter's error indicator is now always normalized. This means
+  that :c:func:`PyErr_SetObject`, :c:func:`PyErr_SetString` and the other
+  functions that set the error indicator now normalize the exception
+  before storing it. (Contributed by Mark Shannon in :gh:`101578`.)
+
 Deprecated
 ----------