[Nginx] Refresh cipher suites (#3669)

Also turn ssl_prefer_server_ciphers off.
"The cipher suites are all strong and so we allow the client to choose, as they will know best if they have support for hardware-accelerated AES" - https://wiki.mozilla.org/Security/Server_Side_TLS#Intermediate_compatibility_.28recommended.29

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

@@ -4,8 +4,8 @@
   override_charset on;
 
   ssl_protocols TLSv1.2 TLSv1.3;
-  ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256';
-  ssl_prefer_server_ciphers on;
+  ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384;
+  ssl_prefer_server_ciphers off;
   ssl_session_cache shared:SSL:50m;
   ssl_session_timeout 1d;
   ssl_session_tickets off;