Stop using Ansible's cron module

This is mainly to address SSL renewal not working for us due to:
- https://github.com/ansible/ansible/issues/71213
- https://github.com/ansible/ansible/pull/71207

Using the cron module was hacky anyway. We shouldn't need an extra
level of buggy abstraction to manage a cronjob file.

roles/matrix-coturn/templates/cron.d/matrix-coturn-ssl-reload.j2

@@ -0,0 +1 @@
+20 4 */5 * * root {{ matrix_host_command_systemctl }} reload matrix-coturn.service