atomic: remove update_ostree_summary_file func
    
    This is now handled by the sync script [1].
    
    [1] https://infrastructure.fedoraproject.org/cgit/ansible.git/tree/roles/bodhi2/backend/files/new-updates-sync#n151
    
    Signed-off-by: Dusty Mabe <dusty@dustymabe.com>