Use new API available in ICU65.1 so legacy locales won't be hidden.

Bug: v8:9312,chromium:968269
Change-Id: I6e44501249cdb863ff9b1ab858efdf8908380a82
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2131373
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66957}