do not enable HSTS for subdomains

nginx.tmpl

@@ -158,7 +158,7 @@ server {
 	{{ end }}
 
 	{{ if (ne $https_method "noredirect") }}
-	add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
+	add_header Strict-Transport-Security "max-age=31536000";
 	{{ end }}
 
 	{{ if (exists (printf "/etc/nginx/vhost.d/%s" $host)) }}