[stable27] Change master version to 29 in tests

[backportbot[bot]]

Backport of #526

Warning, This backport's changes differ from the original and might be incomplete ⚠️

Todo

• [x] Review and resolve any conflicts

• [x] Remove all the empty commits

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.