Update release notes for release 1.1.2 (#319)

Author: llucax

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
-
-<!-- Here goes the main new features and examples or instructions on how to use them -->
-
 ## Bug Fixes
 
 - `FileWatcher`: Fixed `ready()` method to return False when an error occurs. Before this fix, `select()` (and other code using `ready()`) never detected the `FileWatcher` was stopped and the `select()` loop was continuously waking up to inform the receiver was ready.