Prepare for release v1.6.0 (#366)

Author: shsms

RELEASE_NOTES.md

@@ -1,17 +1,5 @@
 # Frequenz channels Release Notes
 
-## Summary
-
-<!-- Here goes a general summary of what this release is about -->
-
-## Upgrading
-
-<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
-
 ## New Features
 
 - Added a `Receiver.close()` method for closing just a receiver.  Also implemented it for all the `Receiver` implementations in this library.
-
-## Bug Fixes
-
-<!-- Here goes notable bug fixes that are worth a special mention or explanation -->