Update changelog

Author: T4rk1n

CHANGELOG.md

@@ -6,6 +6,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ## Fixed
 - [#3278](https://github.com/plotly/dash/pull/3278) Fix loading selector with children starting at the same digit. Fix [#3276](https://github.com/plotly/dash/issues/3276)
+- [#3280](https://github.com/plotly/dash/pull/3280) Remove flask typing import not available in earlier versions.
 
 ## [3.0.3] - 2025-04-14