Update changelog to add instructions for AGP 8.5 and lower

Author: liamjones

CHANGELOG.md

@@ -4,7 +4,7 @@
 * None
 
 ### Enhancements
-* 16KB page size support for Android 15+ ([#7019](https://github.com/realm/realm-js/pull/7019)).
+* 16KB page size support for Android 15+ ([#7019](https://github.com/realm/realm-js/pull/7019)). If you are using Android Gradle Plugin (AGP) 8.5 or lower, you will need to [enable legacy packaging](https://developer.android.com/guide/practices/page-sizes#update-packaging). 
 
 ### Fixed
 * <How to hit and notice issue? what was the impact?> ([#????](https://github.com/realm/realm-js/issues/????), since v?.?.?)