chore(README): remove link to short tutorial
chore(README): remove link to short tutorial

johoelzl/lean,Kha/lean,leodemoura/lean,dselsam/lean,Kha/lean,leodemoura/lean,leodemoura/lean,avigad/lean,rlewis1988/lean,avigad/lean,avigad/lean,leanprover/lean,Kha/lean,Kha/lean,fgdorais/lean,dselsam/lean,fpvandoorn/lean,leanprover-community/lean,leanprover/lean,Kha/lean,digama0/lean,Kha/lean,fgdorais/lean,digama0/lean,rlewis1988/lean,dselsam/lean,fgdorais/lean,leanprover/lean,rlewis1988/lean,leanprover-community/lean,dselsam/lean,avigad/lean,fgdorais/lean,avigad/lean,fpvandoorn/lean,leanprover/lean,rlewis1988/lean,digama0/lean,leanprover-community/lean,leanprover/lean,leanprover/lean,fpvandoorn/lean,johoelzl/lean,johoelzl/lean,johoelzl/lean,fpvandoorn/lean,leodemoura/lean,digama0/lean,fgdorais/lean,fpvandoorn/lean,johoelzl/lean,digama0/lean,dselsam/lean,rlewis1988/lean,leanprover-community/lean,dselsam/lean,fpvandoorn/lean,digama0/lean,leanprover-community/lean,leodemoura/lean,rlewis1988/lean,leodemoura/lean,fgdorais/lean,johoelzl/lean,leanprover-community/lean,avigad/lean