Update changelog

Author: senekor

CHANGELOG.md

@@ -20,6 +20,7 @@
 - Avoid initializing a nested Git repository [@senekor](https://github.com/senekor)
 - `vecs2`: Removed the use of `map` and `collect`, which are only taught later.
 - `structs3`: Rewrote the exercise to make users type method syntax themselves.
+- Rename the exercises for smart pointers and conversions so they're sorted alphabetically. [@foxfromworld](https://github.com/foxfromworld)
 
 ## 6.5.0 (2025-08-21)