fix(library/type_context): is_def_eq_proof_irrel was not symmetric
fix(library/type_context): is_def_eq_proof_irrel was not symmetric

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