Update changelog

Author: mathbunnyru

CHANGELOG.md

@@ -3,6 +3,12 @@
 This changelog only contains breaking and/or significant changes manually introduced to this repository (using Pull Requests).
 All image manifests can be found in [the wiki](https://github.com/jupyter/docker-stacks/wiki).
 
+## 2025-04-01
+
+Affected: all images.
+
+- **Non-breaking:** Apply and merge tags in the same place ([#2274](https://github.com/jupyter/docker-stacks/pull/2274)).
+
 ## 2025-03-23
 
 Affected: `tensorflow-notebook`.