Add changelog entry

Author: luca3rd

src/lightning_app/CHANGELOG.md

@@ -23,6 +23,10 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Added support for adding requirements to commands and installing them when missing when running an app command ([#15198](https://github.com/Lightning-AI/lightning/pull/15198)
 - Added Lightning CLI Connection to be terminal session instead of global ([#15241](https://github.com/Lightning-AI/lightning/pull/15241)
 
+## Changed
+
+- Removed the `--instance-types` option when creating clusters ([#15314](https://github.com/Lightning-AI/lightning/pull/15314))
+
 ### Fixed
 
 - Fixed an issue when using the CLI without arguments ([#14877](https://github.com/Lightning-AI/lightning/pull/14877))