Fix letsencrypt-apache URL

deploy/apache.conf

@@ -38,7 +38,7 @@ Define MUSIC_DIRECTORY_PATH /srv/funkwhale/data/music
    # lines and move the configuration to the previous server block if you
    # don't want to run funkwhale behind https (this is not recommanded)
    # have a look here for let's encrypt configuration:
-   # https://certbot.eff.org/all-instructions/#debian-9-stretch-nginx
+   # https://certbot.eff.org/lets-encrypt/debianstretch-apache.html
    SSLEngine on
    SSLProxyEngine On
    SSLCertificateFile /etc/letsencrypt/live/${funkwhale-sn}/fullchain.pem