Update release_notes.md

Author: newtork

release_notes.md

@@ -16,7 +16,7 @@
 
 ### 📈 Improvements
 
-- 
+- Enable Retry behavior for HttpClient5 instances, to mirror legacy behvior for HttpClient4: `1` retry with `1s` delay for response codes `429` (Too Many Requests) and `503` (Service Unavailable).
 
 ### 🐛 Fixed Issues