Update CHANGELOG for 10.3.1.0

Author: popescu-v

CHANGELOG.md

@@ -6,7 +6,7 @@
   - Example: 10.2.1.4 is the 5th version that supports khiops 10.2.1.
 - Internals: Changes in *Internals* sections are unlikely to be of interest for data scientists.
 
-## Unreleased
+## 10.3.1.0 - 2025-04-16
 
 ### Added
 - (`sklearn`) Support for boolean and float targets in `KhiopsClassifier`.