Use the latest translations for nightly builds

We should set the nightly builds to use the latest commit available, so that translators can have a feedback sooner.

This is already possible for Fenix and base-browser, which use the translation repo directly.

Torbutton still relies on the import scripts, but we can do that after we merge the translations in tor-browser.git (tor-browser#40924, either with or without switching to Fluent, yet).