refactor(library/data/list/perm): use by_cases instead of dependent-if
refactor(library/data/list/perm): use by_cases instead of dependent-if

Kha/lean,soonhokong/lean-osx,fgdorais/lean,soonhokong/lean,c-cube/lean,soonhokong/lean-osx,fpvandoorn/lean2,sp3ctum/lean,soonhokong/lean,leanprover/lean,leodemoura/lean,fpvandoorn/lean,leanprover-community/lean,UlrikBuchholtz/lean,c-cube/lean,avigad/lean,soonhokong/lean-osx,fpvandoorn/lean,sp3ctum/lean,javra/lean,htzh/lean,leodemoura/lean,johoelzl/lean,soonhokong/lean,fgdorais/lean,c-cube/lean,c-cube/lean,eigengrau/lean,eigengrau/lean,Kha/lean,rlewis1988/lean,Kha/lean,fpvandoorn/lean,digama0/lean,dselsam/lean,dselsam/lean,htzh/lean,leodemoura/lean,soonhokong/lean-windows,levnach/lean,fpvandoorn/lean,soonhokong/lean,htzh/lean,johoelzl/lean,soonhokong/lean-osx,fgdorais/lean,soonhokong/lean,leanprover-community/lean,Kha/lean,htzh/lean,johoelzl/lean,leanprover/lean,dselsam/lean,javra/lean,digama0/lean,UlrikBuchholtz/lean,avigad/lean,fgdorais/lean,rlewis1988/lean,soonhokong/lean-windows,leanprover/lean,rlewis1988/lean,rlewis1988/lean,eigengrau/lean,javra/lean,UlrikBuchholtz/lean,c-cube/lean,avigad/lean,soonhokong/lean-windows,fgdorais/lean,fpvandoorn/lean2,levnach/lean,leanprover-community/lean,leanprover/lean,sp3ctum/lean,leodemoura/lean,soonhokong/lean-windows,dselsam/lean,leanprover-community/lean,htzh/lean,fpvandoorn/lean,dselsam/lean,johoelzl/lean,eigengrau/lean,digama0/lean,fpvandoorn/lean2,dselsam/lean,avigad/lean,soonhokong/lean-windows,leodemoura/lean,Kha/lean,eigengrau/lean,levnach/lean,levnach/lean,leanprover/lean,digama0/lean,rlewis1988/lean,UlrikBuchholtz/lean,fgdorais/lean,leodemoura/lean,leanprover/lean,javra/lean,Kha/lean,leanprover-community/lean,fpvandoorn/lean,leanprover-community/lean,fpvandoorn/lean2,fpvandoorn/lean2,soonhokong/lean-osx,javra/lean,UlrikBuchholtz/lean,rlewis1988/lean,digama0/lean,avigad/lean,sp3ctum/lean,digama0/lean,levnach/lean,avigad/lean,johoelzl/lean,johoelzl/lean,sp3ctum/lean