Add the quiet switch to the certbot command

It sends some messages to stderr otherwise

```
  -q, --quiet           Silence all output except errors. Useful for
                        automation via cron. Implies --non-interactive.
                        (default: False)
```

site-cookbooks/kosmos-base/recipes/letsencrypt.rb

@@ -90,5 +90,5 @@ cron "certbot" do
   hour "0,12"
   minute 0
   mailto "ops@kosmos.org"
-  command "cronic /usr/bin/certbot renew"
+  command "cronic /usr/bin/certbot renew -q"
 end