Configuring webcron still fails for some existing clusters

To fix #1118 (closed), we changed the way we configure the Nextcloud cron setting, from occ config:importing a json file to running occ config:app:set. However, the new way fails for some existing clusters (at least staging.stackspin.net):

You are about to set config value core/backgroundjobs_mode as STRING

This might break thing, affect performance on your instance or its security!
Confirm this action by typing 'yes': 
            
  Aborted.

We'll need to programmatically type yes here to allow this to continue.