Typo in README

README.md

@@ -28,7 +28,7 @@ Add the public key to `authorized_keys` for the ACME server's `autocert` user wi
 ssh-copy-id -i cert-retrieval autocert@acme.gsc.org.uk
 ```
 
-Retrieve the keys on a schedule with cron, by setting a crontab entry like the following:
+Retrieve the certificates on a schedule with cron, by setting a crontab entry like the following:
 
 ```bash
 # m h  dom mon dow    command