Update changelog

CHANGELOG.rst

 Unreleased changes
 ------------------
+
+Version 2
+---------
+
+2.2.4 / 2022-12-15
+~~~~~~~~~~~~~~~~~~
 * `log_analyser.py` now also parses gzipped log files
 * Several backend scripts now also log the memory consuption
 * Fixes memory issues in several backend scrripts, which were
   introduced in MatplotLib 3.5.2
-
-Version 2
----------
+* Updated km3pipe to 9.13.8 and km3db to 0.11.1 in the backend
 
 2.2.3 / 2022-11-20
 ~~~~~~~~~~~~~~~~~~