Configuring webcron fails

With the upgrade to Nextcloud 29, we're hitting this regression: https://github.com/nextcloud/server/issues/45083 . There is a PR to fix that, but 1. it might not be backported to 29 and 2. it's not sure it will fix our method of configuring using php occ config:import. So for now I'll attempt to use the workaround mentioned in the issue, of setting the config value using

occ config:app:set --value webcron --type string core backgroundjobs_mode