fix(frontends/lean/dependencies): compilation warning
fix(frontends/lean/dependencies): compilation warning

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

dselsam/lean,leanprover/lean,leodemoura/lean,rlewis1988/lean,fpvandoorn/lean,fgdorais/lean,levnach/lean,rlewis1988/lean,htzh/lean,c-cube/lean,soonhokong/lean,fpvandoorn/lean,leanprover/lean,sp3ctum/lean,dselsam/lean,johoelzl/lean,soonhokong/lean-osx,avigad/lean,c-cube/lean,javra/lean,leanprover/lean,leanprover-community/lean,javra/lean,leanprover-community/lean,rlewis1988/lean,javra/lean,Kha/lean,Kha/lean,soonhokong/lean-osx,leanprover-community/lean,c-cube/lean,eigengrau/lean,fpvandoorn/lean,Kha/lean,rlewis1988/lean,rlewis1988/lean,avigad/lean,dselsam/lean,johoelzl/lean,soonhokong/lean-windows,johoelzl/lean,fgdorais/lean,soonhokong/lean-windows,UlrikBuchholtz/lean,fgdorais/lean,levnach/lean,Kha/lean,htzh/lean,levnach/lean,leodemoura/lean,soonhokong/lean-windows,dselsam/lean,digama0/lean,johoelzl/lean,soonhokong/lean-windows,fpvandoorn/lean,soonhokong/lean-osx,leodemoura/lean,UlrikBuchholtz/lean,leodemoura/lean,eigengrau/lean,fpvandoorn/lean2,leanprover-community/lean,leanprover-community/lean,UlrikBuchholtz/lean,soonhokong/lean-windows,digama0/lean,leanprover/lean,fgdorais/lean,dselsam/lean,digama0/lean,Kha/lean,fgdorais/lean,johoelzl/lean,johoelzl/lean,digama0/lean,fpvandoorn/lean,soonhokong/lean,eigengrau/lean,sp3ctum/lean,UlrikBuchholtz/lean,sp3ctum/lean,htzh/lean,leanprover/lean,levnach/lean,eigengrau/lean,fgdorais/lean,htzh/lean,avigad/lean,htzh/lean,sp3ctum/lean,dselsam/lean,fpvandoorn/lean2,soonhokong/lean,c-cube/lean,digama0/lean,eigengrau/lean,c-cube/lean,soonhokong/lean-osx,avigad/lean,leanprover/lean,javra/lean,Kha/lean,levnach/lean,leanprover-community/lean,soonhokong/lean-osx,leodemoura/lean,soonhokong/lean,fpvandoorn/lean2,leodemoura/lean,soonhokong/lean,digama0/lean,fpvandoorn/lean2,fpvandoorn/lean,UlrikBuchholtz/lean,avigad/lean,avigad/lean,sp3ctum/lean,javra/lean,rlewis1988/lean,fpvandoorn/lean2