Update changelog with pull request yiisoft#20296

Author: Mārtiņš Briedis

framework/CHANGELOG.md

@@ -22,6 +22,7 @@ Yii Framework 2 Change Log
 - Bug #20140: Fix compatibility with PHP 8.4: calling `session_set_save_handler()` (Izumi-kun)
 - New #20185: Add `BackedEnum` support to `AttributeTypecastBehavior` (briedis)
 - Bug #17365: Fix "Trying to access array offset on null" warning (xcopy)
+- Bug #20296: Fix broken enum test (briedis)
 
 2.0.51 July 18, 2024
 --------------------