Update notes after release (frequenz-floss#115)

Author: flora-hofmann-frequenz

RELEASE_NOTES.md

@@ -6,10 +6,7 @@
 
 ## Upgrading
 
-This update comes with a breaking change, that originates from a breaking change in the API specs. Specifically:
-* This and later versions of the client can only be used with the latest reporting API service >=v0.7 but not with older versions of the service.
-* Older versions of the client can only be used with the reporting API service versions < v0.7 but no later versions.
-To ensure compatibility, both the client and service must be updated simultaneously.
+<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
 
 ## New Features