Fi and fl glyphs to be treated secondary

If a font has a set of [f_i f_l] or [f_i.liga f_l.liga] together with [fi fl], they are both used in the liga feature, which seems redundant. I think only one context should be used, and the underscore ones be prioritised. In my opinion, the Unicode fi and fl cause more trouble and therefore be a secondary option when there’s no underscore-named versions are unavailable.

Fixed it.