Update agreement URL; pointed out by sthen.

OK benno, sthen

src/etc/acme-client.conf

@@ -1,14 +1,14 @@
 #
-# $OpenBSD: acme-client.conf,v 1.4 2017/03/22 11:14:14 benno Exp $
+# $OpenBSD: acme-client.conf,v 1.5 2017/11/15 12:22:45 florian Exp $
 #
 authority letsencrypt {
-        agreement url "https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf"
+        agreement url "https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.pdf"
         api url "https://acme-v01.api.letsencrypt.org/directory"
         account key "/etc/acme/letsencrypt-privkey.pem"
 }
 
 authority letsencrypt-staging {
-        agreement url "https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf"
+        agreement url "https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.pdf"
         api url "https://acme-staging.api.letsencrypt.org/directory"
         account key "/etc/acme/letsencrypt-staging-privkey.pem"
 }