chore(src/CMakeLists): prepare for next release
chore(src/CMakeLists): prepare for next release

(not that we're currently planning for one in the 3.x series)
fpvandoorn/lean,Kha/lean,dselsam/lean,leanprover-community/lean,digama0/lean,dselsam/lean,leanprover-community/lean,fpvandoorn/lean,fpvandoorn/lean,leodemoura/lean,Kha/lean,leodemoura/lean,leanprover/lean,dselsam/lean,fpvandoorn/lean,leodemoura/lean,Kha/lean,leanprover-community/lean,leanprover-community/lean,digama0/lean,leanprover/lean,leanprover/lean,fpvandoorn/lean,dselsam/lean,leanprover/lean,leanprover/lean,Kha/lean,leodemoura/lean,digama0/lean,leodemoura/lean,leodemoura/lean,dselsam/lean,digama0/lean,leanprover-community/lean,leanprover-community/lean,Kha/lean,digama0/lean,fpvandoorn/lean,Kha/lean,leanprover/lean,dselsam/lean,digama0/lean