Sync with https://github.com/tc39/proposal-unified-intl-numberformat/pull/54

Bug: v8:9483
Change-Id: I2aec5a78be235bddd4faa568665b73b9b84d7c93
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1700426Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62819}