fix(algebra/group.lean): remove unnecessary use of add.assoc from theorem bit0_add_bit1_helper
fix(algebra/group.lean): remove unnecessary use of add.assoc from theorem bit0_add_bit1_helper

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