Nginx: Update the http2 directive.

It's no longer a part of the listen directive but a standalone one.

nginx/conf.d/default.conf

@@ -7,8 +7,9 @@ server {
 }
 
 server {
-    listen      443 ssl http2 default_server;
-    listen      [::]:443 ssl http2 default_server;
+    listen      443 ssl default_server;
+    listen      [::]:443 ssl default_server;
+    http2       on;
     include     snippets/ssl-legacy.conf;
     location    / { return 301 https://www.shore.co.il$request_uri; }
 }