Fix subdomain basic example

nginx/subdomain.conf

@@ -7,16 +7,12 @@ server {
   location / {
     try_files $uri $uri/;
   }
-}
 
-server {
-  root MY_ROOT;
   if ($host = DOMAIN) {
       return 301 https://$host$request_uri;
   } # managed by Certbot
 
   listen 80;
   listen [::]:80;
-  server_name DOMAIN;
   return 404; # managed by Certbot
 }