Update release notes

Signed-off-by: Sahas Subramanian <[email protected]>

Author: shsms

RELEASE_NOTES.md

@@ -1,17 +1,5 @@
 # Frequenz Microgrid API Client 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
-
-<!-- Here goes notable bug fixes that are worth a special mention or explanation -->
+- Widen `frequenz-client-base` dependency to allow `v0.9.0`.