add note in changelog

Author: littleaj

CHANGELOG.md

@@ -38,6 +38,7 @@
 
 # Version 2.4.1
 - Fix [#910](https://github.com/microsoft/ApplicationInsights-Java/issues/910) Fixed correlation id serialization.
+- Upgraded spring boot dependencies in spring-boot-starter from 1.5.9 to 1.5.21.
 
 # Version 2.4.0
 - Updated Spring Boot Starter version number to track with the SDK version.