Prepare release notes for v0.18.0

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 release focuses on finishing the automation of dependabot updates, adding more automated upgrade workflows and fixing some problems with the previous 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.
@@ -16,14 +14,8 @@ All upgrading should be done via the migration script or regenerating the templa
 curl -sSLf https://raw.githubusercontent.com/frequenz-floss/frequenz-repo-config-python/<tag>/cookiecutter/migrate.py | python3 -I
 ```
 
-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
 
 - The cookiecutter now asks whether a repository is private, defaults that answer from the selected license, and uses it to toggle private-repository workflow behavior, public publishing jobs, and the link to GitHub Discussions in the issue template chooser.
@@ -36,8 +28,6 @@ But you might still need to adapt your code:
 
 ## Bug Fixes
 
-<!-- Here goes notable bug fixes that are worth a special mention or explanation -->
-
 ### Cookiecutter template
 
 - The unused cross-arch QEMU-based testing infrastructure has been removed. The `.github/containers/nox-cross-arch/` and `.github/containers/test-installation/` directories, as well as the "Cross-Arch Testing" section in `CONTRIBUTING.md`.