Split Python versions note into two under separate headings

CHANGES.txt

@@ -1,12 +1,21 @@
 3.0.1 (2024-11-28)
 ------------------
 
-Security
+Backward Incompatibilities
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Python 3.8 is no longer supported.
+  See https://github.com/Pylons/waitress/pull/445.
+
+Features
 ~~~~~~~~
 
-- Python 3.8 is no longer supported. Added support for Python 3.13.
+- Added support for Python 3.13.
   See https://github.com/Pylons/waitress/pull/445.
 
+Security
+~~~~~~~~
+
 - Fix a bug that would lead to Waitress busy looping on select() on a half-open
   socket due to a race condition that existed when creating a new HTTPChannel.
   See https://github.com/Pylons/waitress/pull/435,