Reduce the number of locales we provide updates for in nightly
Making updates available for each locale is costing time on nightly build/signing machines:
- generating the .mar files
- generating the incremental .mar files
- transferring the mar files between hosts to sign them and publish them
With the current resources we have, I think it risks increasing the time to provide updates on nightly builds too much. I think we could start by providing updates for a subset of locales only, and think about increasing that list later.