FreeBSD automatic renewal documentation is incorrect

The website says:
```
The command to renew certbot is installed in one of the following locations:

    /etc/crontab/
    /etc/cron.*/*
    systemctl list-timers

```

The above is incorrect. And systemctl isn't a FreeBSD command at all. The correct entry is that py-certbot package installs the automatic update script here:
```
/usr/local/etc/periodic/weekly/500.certbot-3.11
```