Problematic practice exercises

While adding test templates as described in #465, we keep finding some very old exercises that are wildly unlike the canonical version.

So far:
- Allergies ✅
- Crypto Square
- Triangle ✅
- Tournament

No doubt there will be others. We're not talking minor variations. For example, Crypto Square requires implementation of 4 functions, not the canonical single function.

I don't want anyone wasting time trying to beat these into submission. Maybe we can add some extra tests manually, but I don't even see what `tests.toml` is doing in these cases, and we'll never automate them.

Should we mark them in some way, such as adding an empty `.meta/.notemplate` file?

No big worry. If we can template at least half the 85 active exercises and all the new ones going forward, I call that a win.