Remove next-i18next as a dependency

[sawyerh]

Blockers

This ticket needs done in coordination with the larger effort to migrate to the Next.js App Router: #66

Details

This is based on a comment from the maintainer of next-i18next:

It just means next-i18next is not necessary anymore:
https://locize.com/blog/next-13-app-dir-i18n/
https://github.com/i18next/next-13-app-dir-i18next-example

My read of this is that next-i18next will only remain relevant for sites using the "pages" router.

[sawyerh]

This will happen as part of the migration to the App Router, which includes a move to using next-intl instead of i18next