fix(library/attribute_manager): memory leak
fix(library/attribute_manager): memory leak

The method `release` releases the pointer ownership without deleting it.

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