Don't expose nginx version with each response

roles/matrix-nginx-proxy/templates/nginx/nginx.conf.j2

@@ -48,6 +48,8 @@ http {
 
 	keepalive_timeout 65;
 
+	server_tokens off;
+
 	#gzip on;
 	{# Map directive needed for proxied WebSocket upgrades #}
 	map $http_upgrade $connection_upgrade {