This shipped in v7.9, which is stable since six weeks. We do not test
the previous configuration any more and don't plan to move back, hence
remove the flag and clean up the code.

R=ahaas@chromium.org

Bug: v8:10155
Change-Id: I6b981f4be686473a911f041952cb684749d9fe7e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2030732
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66063}