Add mr version improvement to changelog

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

CHANGELOG

@@ -127,6 +127,9 @@ v 8.12.4
   - Fix failed project deletion when feature visibility set to private. !6688
   - Prevent claiming associated model IDs via import.
   - Set GitLab project exported file permissions to owner only
+  - Improve the way merge request versions are compared with each other
+
+v 8.12.4 (unreleased)
 
 v 8.12.3
   - Update Gitlab Shell to support low IO priority for storage moves