Update Release Notes

Signed-off-by: camille-bouvy-frequenz <[email protected]>

Author: camille-bouvy-frequenz

RELEASE_NOTES.md

@@ -13,6 +13,8 @@
 * Extra validation check to ensure the quantity is strictly positive.
 * Extra validation check to ensure the quantity and price are within the allowed bounds.
 * Add more edge cases to the integration tests
+* Add a module defining a backoff strategy to handle retries with increasing timeouts.
+* Use the backoff strategy when calling gRPCs in the Client
 
 ## Bug Fixes