Update changelog

Author: jsignell

CHANGELOG.md

@@ -32,6 +32,7 @@
 - Use `from __future__ import annotations` for type signatures ([#962](https://github.com/stac-utils/pystac/pull/962))
 - Use `TypeVar` for alternate constructors ([#983](https://github.com/stac-utils/pystac/pull/983))
 - Behavior when required fields are missing in `Item.from_dict` ([#994](https://github.com/stac-utils/pystac/pull/994))
+- By default, `ItemCollection` now clones items in iterator (`clone_items=True`) ([#1016](https://github.com/stac-utils/pystac/pull/1016))
 
 ### Fixed