Avoid attempting to clean up an OBS branch twice

The comment in 'after_script' is actually no longer valid, because it now uploads the cleanup-project-branch artifact whether or not the build succeeded. As a result, the cleanup job still runs and attempts to remove the branch, even though it was already removed in the after_script.

https://phabricator.apertis.org/T7890

Signed-off-by: Ryan Gonzalez ryan.gonzalez@collabora.com