Remove Home tab

Remove the "Home" tab as this is already available via clicking on the
ATLAS site icon (and this is where intuitively most users will expect
it).

mkdocs.yml

@@ -39,7 +39,6 @@ extra_css:
   - stylesheets/extra.css
 
 nav:
-  - Home: index.md
   - Athena:
     - Athena basics: 
       - athena/basics/index.md