Update v_0_3_9.md

Author: david-leifker

docs/managed-datahub/release-notes/v_0_3_9.md

@@ -17,6 +17,7 @@ Helm Chart
 
 - OpenAPI Async Timeseries Aspects will not automatically create the entity's key aspect.
 - Writes for hard deleted entities will be dropped for 60 seconds after the hard delete is processed.
+- API Tracing is considered as a beta release
 
 ## Release Changelog
 ---