complete release note

Author: philon-msft

docs/ReleaseNotes.md

@@ -8,7 +8,7 @@ Current package versions:
 
 ## Unreleased
 
-- Update default Redis version from 4.0.0 to 6.0.0 for Azure Redis resources
+- Update default Redis version from 4.0.0 to 6.0.0 for Azure Redis resources ([#2810 by philon-msft](https://github.com/StackExchange/StackExchange.Redis/pull/2810))
 
 ## 2.8.16