fix(library/data/set/basic): make set_of reducible
fix(library/data/set/basic): make set_of reducible

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