Update changelog

CHANGELOG.rst

@@ -6,6 +6,16 @@ All notable changes to this project will be documented in this file.
 The format is based on `Keep a Changelog`_,
 and this project adheres to `Semantic Versioning`_.
 
+Unreleased
+----------
+
+Upgrade notice
+~~~~~~~~~~~~~~
+
+If you're upgrading from 3.x, there is now a migration path to use.
+Therefore, please install ``AlekSIS-App-Lesrooster`` which now
+includes parts of the legacy Chronos and the migration path.
+
 `4.0.0.dev3`_ - 2024-07-10
 --------------------------
 
@@ -38,8 +48,7 @@ Starting from the class register core functionality, Alsijil is getting a entire
 of both its frontend and backend. The models formerly used for lesson documentation, notably
 `LessonDocumentation` and `PersonalNote` are replaced by new ones based on the calendar framework
 provided by `AlekSIS-Core` and the absense framework provided by `AlekSIS-App-Kolego`. The legacy
-views providing management functionality for those legacy models are not available anymore. Currently,
-there exists no migration path away from legacy data.
+views providing management functionality for those legacy models are not available anymore.
 
 Changed
 ~~~~~~~