Prepare release notes for v0.16.0

Signed-off-by: Leandro Lucarella <luca-frequenz@llucax.com>

Author: llucax

RELEASE_NOTES.md

@@ -2,12 +2,10 @@
 
 ## Summary
 
-<!-- Here goes a general summary of what this release is about -->
+This is a maintenance, template-only, bugfix release.
 
 ## Upgrading
 
-<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
-
 ### Cookiecutter template
 
 All upgrading should be done via the migration script or regenerating the templates.
@@ -16,22 +14,8 @@ All upgrading should be done via the migration script or regenerating the templa
 curl -sSL https://raw.githubusercontent.com/frequenz-floss/frequenz-repo-config-python/v0.16.0/cookiecutter/migrate.py | python3
 ```
 
-But you might still need to adapt your code:
-
-<!-- Here upgrade steps for cookiecutter specifically -->
-
-## New Features
-
-<!-- Here goes the main new features and examples or instructions on how to use them -->
-
-### Cookiecutter template
-
-<!-- Here new features for cookiecutter specifically -->
-
 ## Bug Fixes
 
-<!-- Here goes notable bug fixes that are worth a special mention or explanation -->
-
 ### Cookiecutter template
 
 - Added a migration step for api repositories to fix `mkdocs.yml` when the previous `mkdocstrings-python` v2 migration moved only `paths: ["src"]` under `handlers.python.options` but not `paths: ["py"]`.