fix(library/mt_task_queue): reverse dependencies may already be queued
fix(library/mt_task_queue): reverse dependencies may already be queued

When we check whether the dependencies for a task have already been
evaluated and then accordingly move the task from waiting to queued, we
do not remove it from the reverse dependency lists it appears in.

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