use schedure resource instead of cron

https://gitlab.adullact.net/adullact/puppet-wordpress/blob/master/manifests/external_fact.pp#L45

https://puppet.com/docs/puppet/4.10/types/schedule.html

https://puppet.com/docs/puppet/5.0/types/schedule.html

https://puppet.com/docs/puppet/6.0/types/schedule.html