Fix the structure of os

mkdocs.yml

 site_name: "storage"
 
 nav:
+  - Data Storage Services: ./index.md
   - Object Storage Services: 
     - Overview: ./object-storage/index.md
     - S3 Service: ./object-storage/s3-service.md

object-storage/index.md

@@ -29,5 +29,9 @@ Object Storage Services is a portfolio of services allowing to facilitate your a
 
     [:octicons-arrow-right-24: Owncloud](https://du.cesnet.cz/en/navody/owncloud/start)  
  
+<!---    
+[:octicons-arrow-right-24: Account properties and lifecycle](/account/properties)   
+--->
+
 </div>