fix(examples/lean): typo
fix(examples/lean): typo

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

Kha/lean,leanprover-community/lean,soonhokong/lean-windows,eigengrau/lean,eigengrau/lean,soonhokong/travis_test,avigad/lean,leodemoura/lean,digama0/lean,soonhokong/lean-windows,Kha/lean,leodemoura/lean,fgdorais/lean,UlrikBuchholtz/lean,soonhokong/lean-osx,digama0/lean,codyroux/lean0.1,levnach/lean,leodemoura/lean,johoelzl/lean,sp3ctum/lean,fpvandoorn/lean2,javra/lean,leanprover-community/lean,rlewis1988/lean,soonhokong/lean,fpvandoorn/lean2,leanprover-community/lean,soonhokong/travis_test,sp3ctum/lean,fgdorais/lean,sp3ctum/lean,avigad/lean,Kha/lean,htzh/lean,codyroux/lean0.1,leanprover/lean,soonhokong/lean-osx,fpvandoorn/lean2,dselsam/lean,eigengrau/lean,digama0/lean,johoelzl/lean,eigengrau/lean,codyroux/lean0.1,UlrikBuchholtz/lean,avigad/lean,fgdorais/lean,sp3ctum/lean,levnach/lean,fpvandoorn/lean2,javra/lean,soonhokong/lean-windows,levnach/lean,javra/lean,soonhokong/lean,dselsam/lean,fgdorais/lean,c-cube/lean,rlewis1988/lean,c-cube/lean,johoelzl/lean,leanprover-community/lean,soonhokong/lean-windows,digama0/lean,fpvandoorn/lean2,htzh/lean,fpvandoorn/lean,rlewis1988/lean,fpvandoorn/lean,johoelzl/lean,soonhokong/lean,htzh/lean,fpvandoorn/lean,dselsam/lean,avigad/lean,digama0/lean,codyroux/lean0.1,htzh/lean,rlewis1988/lean,johoelzl/lean,soonhokong/lean,leodemoura/lean,soonhokong/travis_test,leanprover/lean,fgdorais/lean,rlewis1988/lean,UlrikBuchholtz/lean,eigengrau/lean,javra/lean,c-cube/lean,leodemoura/lean,fgdorais/lean,fpvandoorn/lean,c-cube/lean,UlrikBuchholtz/lean,levnach/lean,leanprover/lean,leanprover/lean,dselsam/lean,leodemoura/lean,leanprover/lean,fpvandoorn/lean,leanprover-community/lean,soonhokong/lean-windows,dselsam/lean,fpvandoorn/lean,Kha/lean,Kha/lean,c-cube/lean,Kha/lean,leanprover/lean,levnach/lean,leanprover-community/lean,soonhokong/lean-osx,avigad/lean,digama0/lean,javra/lean,htzh/lean,soonhokong/lean-osx,avigad/lean,dselsam/lean,soonhokong/lean,soonhokong/lean-osx,johoelzl/lean,soonhokong/travis_test,UlrikBuchholtz/lean,rlewis1988/lean,sp3ctum/lean