Generic translations don't always play nicely with form-specific Phrase projects

[shawnbot]

I haven't had time to dig into it, but I discovered a couple of cases in a recent form where strings that we have generic translations checked into git weren't being applied to a form with Phrase translations of its own: the "Next" and "Back" buttons, and generic validation error messages like invalid_email.

There might be a bug in how we're merging the two translation "resource" objects? 🤷