doc(examples/lean): use new Import command in examples
doc(examples/lean): use new Import command in examples

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

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