The tree view uses a connection to rowsInserted internally for updating
the view, so we may only remove our specific connection to updateSize.
Otherwise the view stops showing items after the first rowsInserted.

Task-number: QTCREATORBUG-18522
Change-Id: Ib80fa39ee5556221a447db3556495a3608e3f62b
Reviewed-by: Orgad Shaneh <orgads@gmail.com>