Update release notes

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

RELEASE_NOTES.md

@@ -10,15 +10,15 @@
 
 ### Cookiecutter template
 
-All upgrading should be done via the migration script or regenerating the templates.
+* Branch protection rule **Protect version branches** was updated, please re-import it following the [instructions](https://frequenz-floss.github.io/frequenz-repo-config-python/v0.13/user-guide/start-a-new-project/configure-github/#rulesets).
+
+All other upgrading should be done via the migration script or regenerating the templates.
 
 ```bash
 curl -sSL https://raw.githubusercontent.com/frequenz-floss/frequenz-repo-config-python/v0.12/cookiecutter/migrate.py | python3
 ```
 
-But you might still need to adapt your code:
-
-<!-- Here upgrade steps for cookiecutter specifically -->
+But you might still need to adapt your code.
 
 ## New Features
 
@@ -33,6 +33,16 @@ But you might still need to adapt your code:
     * Major updates and dependencies excluded by the above groups are still managed, but they'll create one PR per dependency, as breakage is expected, so it might need manual intervention.
     * Finally, we group some dependencies that are related to each other, and usually needs to be updated together.
 
+- The GitHub workflows is now split into PRs and CI workflows.
+
+    These new workflows also start using a new reusable `gh-action-nox`, native arm runners and Ubuntu 24.04, as [Ubuntu 20.04 will be removed from GitHub runners by April's 1st][ubuntu-20.04]. Python 3.12 is also added to the test matrix.
+
+    The PR action is more lightweight, and only tests with one matrix (the most widely used), so PRs can be tested more quickly.
+
+    The push workflow does a more intense testing with all matrix combinations. This also runs for the merge queue, so before PRs are actually merged the tests will run for the complete matrix.
+
+[ubuntu-20.04]: https://github.blog/changelog/2025-01-15-github-actions-ubuntu-20-runner-image-brownout-dates-and-other-breaking-changes/
+
 ## Bug Fixes
 
 <!-- Here goes notable bug fixes that are worth a special mention or explanation -->