Revert "enable ipv6 listening"

This reverts commit 9582113c42.

Discussion
9582113c42 (commitcomment-39238032)

etc/nginx/sites-available/site.conf

@@ -1,6 +1,5 @@
 server {
     listen 8080 default_server;
-    listen [::]:8080 default_server;
 
     root /var/www;
     index index.php index.html index.htm;