Remove the style from flag and use value return from ICU object instead.

Change-Id: I89732c4cd9f093136d18fcd1122e8858c6ca50dc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2057975Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66352}