Update deprecated http2 nginx conf syntax (#2174)

Co-authored-by: Luke Moch <luke@mochfamily.com>
Co-authored-by: Franck Nijhof <git@frenck.dev>

Author: 3 people

node-red/rootfs/etc/nginx/templates/direct.gtpl

@@ -2,7 +2,8 @@ server {
     {{ if not .ssl }}
     listen {{ .port }} default_server;
     {{ else }}
-    listen {{ .port }} default_server ssl http2;
+    listen {{ .port }} default_server ssl;
+    http2 on;
     {{ end }}
 
     include /etc/nginx/includes/server_params.conf;