Adding to changelog

Author: rhysrevans3

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Changed
 
 - Elasticsearch drivers from 7.17.9 to 8.11.0 [#169](https://github.com/stac-utils/stac-fastapi-elasticsearch/pull/169)
+- Collection update endpoint no longer delete all sub items [#177](https://github.com/stac-utils/stac-fastapi-elasticsearch/pull/177)
 
 ### Fixed