Change cron type

Because the upstream nextcloud helm chart used to implement cronjobs by kubernetes CronJobs, we set the nextcloud cron type to webcron. At some point since we implemented this, the upstream chart changed and now instead uses a sidecar container that runs a cron daemon. As such we should change the type to cron. We might not even need to do this ourselves, because

At first launch, the background jobs mode in your Nextcloud basic settings will automatically be set to Cron