Add Notebooks update to CHANGELOG for release 3.63.0 (#1424)

Just a follow up to CHANGELOG updates. No need to wait for tests to complete

Author: vbrodsky

CHANGELOG.md

@@ -4,6 +4,9 @@
 * Ability for users to install and use sdk with pydantic v.2.* while still maintaining support for pydantic v1.*
 * `ModelRun` `export()` and `export_v2()` add model_run_details to support splits
 
+## Notebooks
+* Add composite mask notebook
+
 # Version 3.62.0 (2024-02-12)
 ## Added
 * Support custom metrics for predictions (all applicable annotation classes)