Fix "No calls to throwing functions" warnings in unit tests

[mplorentz]

We have a number of No calls to throwing functions occur within 'try' expression warnings in our unit tests. This is because multiple Swift Packages that we import define functions with the same name, and depending on the order they are imported a different version can be used. What's worse is that the implementations aren't equivalent 😭 it caused a bug in the main target with event signing (can't find the details now) and this bug might sneak back in if we don't fix these warnings.

[joshuatbrown]

@mplorentz I used to see these warnings, too, but I'm not any more, so I'm closing this. Maybe this was fixed when we removed some dependencies we no longer needed? Or maybe when someone just fixed them.

[mplorentz]

I think #987 might have fixed this. Thanks!