Drop aum-offline-upgrade-branch test

This test is failing in v2022 since there is no previous branch to use as initial branch. Previously v2022pre was used, but unfortunately it was dropped during cleanup.

It is worth to mention that v2021 uses a different name scheme, with minimal and target as names, causing the test also to fail in case of using it as initial branch.

infrastructure/apertis-issues#418 (closed)

Signed-off-by: Walter Lozano walter.lozano@collabora.com