feat(library/data/nat/div.lean): remove dependence on funext
feat(library/data/nat/div.lean): remove dependence on funext

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