refactor(library/data/list/perm): remove dead code
refactor(library/data/list/perm): remove dead code

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