The page manager shows an advanced structure if the user has multi website
enabled. It will show specific pages as a child of its generic one.
It is useful to directly understand and figure which pages are 'overiden'.
But it doesn't really makes sense for an end user, which doesn't know there is
actually generic and/or specific pages.
It makes more sense to show that behavior only in debug and not in multi
websites, even more since pages are overiden even in mono website.
closesodoo/odoo#68902
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>