Remove Qtile.list_wids and client_from_wids
Remove Qtile.list_wids and client_from_wids

This methods are also dead code. They are used in one place (which is
within `Qtile` itself) and due to changes in the format of
`Qtile.windows_map` the methods are unnecessary.

ramnes/qtile,qtile/qtile,qtile/qtile,ramnes/qtile