Intl.DisplayNames was shipped in m81 and we now can remove the flag.
https://www.chromestatus.com/features/4965112605573120


Bug: v8:8703
Change-Id: Ib65d787c1871aa1da38a22fdb9e369c680c7d2c9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2163820
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67382}