Fix tests to throw an error if missingTranslations: true is set unnecessarily

[quisquous]

Right now the find missing translations script will note if this is set to true when it's not needed. However, test_trigger.ts and test_timeline.ts are not smart enough to be able to figure this out, because the logic is in different files to figure out if something has been missed.

It'd be nice to somehow be able to enforce that missingTranslations: true is only set if there are missing translations. That way it will be obvious when any file is in a "done" or "not done" state, and so it will be obvious in a PR when this state has changed (and so it doesn't happen accidentally).