[Nginx] Drop X-Powered-By via fastcgi_hide_header

data/conf/nginx/includes/site-defaults.conf

@@ -41,6 +41,7 @@
 
   error_log  /var/log/nginx/error.log;
   access_log /var/log/nginx/access.log;
+  fastcgi_hide_header X-Powered-By;
   absolute_redirect off;
   root /web;