Tutorial: start with folded Development subitems in navigation bar

They are not relevant in the tutorial context.

Change-Id: I8c2d563304d9b6fd56778dd240f42dec2f129008
diff --git a/templates/doc/navigation.json b/templates/doc/navigation.json
index b53bcf6..690a3a8 100644
--- a/templates/doc/navigation.json
+++ b/templates/doc/navigation.json
@@ -105,6 +105,7 @@
   {
     "title": "Development",
     "id": "development",
+    "class": "folded",
     "items": [
       {
         "title": "Kalamar",