The flag has been enabled by default for two version now, so it is time
to remove it.

R=binji@chromium.org

Bug: v8:9921
Change-Id: I833e04a3f9d238e7bcf27e93148c9492776af3c6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2402034Reviewed-by: Ben Smith <binji@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70838}