Update CHANGELOG.md

CHANGELOG.md

@@ -15,6 +15,7 @@
 * **Postgres/MySQL/MSSQL**: Use floor rounding in $__timeGroup macro function [#12460](https://github.com/grafana/grafana/issues/12460), thx [@svenklemm](https://github.com/svenklemm)
 * **MySQL/MSSQL**: Use datetime format instead of epoch for $__timeFilter, $__timeFrom and $__timeTo macros [#11618](https://github.com/grafana/grafana/issues/11618) [#11619](https://github.com/grafana/grafana/issues/11619), thx [@AustinWinstanley](https://github.com/AustinWinstanley)
 * **Github OAuth**: Allow changes of user info at Github to be synched to Grafana when signing in [#11818](https://github.com/grafana/grafana/issues/11818), thx [@rwaweber](https://github.com/rwaweber)
+* **Alerting**: Fix diff and percent_diff reducers [#11563](https://github.com/grafana/grafana/issues/11563), thx [@jessetane](https://github.com/jessetane)
 
 # 5.2.2 (unreleased)