fix(frontends/lean/pp): bug in tuple/pair pretty printing
fix(frontends/lean/pp): bug in tuple/pair pretty printing

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

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