chore(build): restrict Travis tasks when building nightlies [skip ci]
chore(build): restrict Travis tasks when building nightlies [skip ci]

fpvandoorn/lean,digama0/lean,leanprover-community/lean,dselsam/lean,dselsam/lean,digama0/lean,digama0/lean,leanprover-community/lean,digama0/lean,fpvandoorn/lean,leanprover-community/lean,leanprover-community/lean,dselsam/lean,digama0/lean,leanprover-community/lean,dselsam/lean,fpvandoorn/lean,fpvandoorn/lean,dselsam/lean,digama0/lean,fpvandoorn/lean,dselsam/lean,fpvandoorn/lean,leanprover-community/lean