reported by @nuttycom

Hey, I just realized that my current Zallet testing is stymied because NU6.1 activated on testnet but the Zaino version we're depending on doesn't yet support it. Zebra's recent releases have been updated, so I decided to give a go at updating Zaino but I found myself somewhat stymied here, because it looks like to really do things properly I also need to update zingolib. We've got a bit of a knot of dependencies here, and I'm wondering what the best approach is to untying it; for example, it looks like zingolib is only needed by zaino-testutils - is there a way that we can prune down the workspace so that we don't run into this kind of issue?