Prepare release notes for next release

Signed-off-by: Elzbieta Kotulska <elzbieta.kotulska@frequenz.com>

RELEASE_NOTES.md

@@ -1,9 +1,5 @@
 # Frequenz Python SDK Release Notes
 
-## Summary
-
-<!-- Here goes a general summary of what this release is about -->
-
 ## Upgrading
 
 - `frequenz.sdk.config.load_config()` doesn't accept classes decorated with `marshmallow_dataclass.dataclass` anymore. You should use the built-in `dataclasses.dataclass` directly instead, no other changes should be needed, the metadata in the `dataclass` fields will still be used.
@@ -13,6 +9,3 @@
 
 - `frequenz.sdk.config.load_config()` can now use a base schema to customize even further how data is loaded.
 
-## Bug Fixes
-
-<!-- Here goes notable bug fixes that are worth a special mention or explanation -->