fix #1899

[cellog]

This change fixes the issue raised by @robintown. The types for Trans did not have a default value for Key, which is what was causing the breakage.

Basically, IcuTrans requires a key, so there is always a value to infer from. For Trans, where the key is optional, the value was inferred as the full ParseKeys<...> type. The bug was introducing a default of = string. This is unnecessary and was the root cause of the problem.

@robintown can you please try this fix on your local codebase and confirm it works?

Checklist

• only relevant code is changed (make a diff before you submit the PR)
• run tests npm run test
• tests are included
• commit message and code follows the Developer's Certification of Origin

[coveralls]

coverage: 97.682%. remained the same
when pulling 346f41f on cellog:issue-1899-fix
into 3b4e102 on i18next:master.

[adrai]

@cellog fyi: the typescript tests fails

[cellog]

I gotchu