AtomicValue is deprecated, so we can start removing things that are not
in use any more.

R=mstarzinger@chromium.org

Bug: v8:8238
Change-Id: I0a1445eccaf89f8869fd56e0fbece809bbcd6e5e
Reviewed-on: https://chromium-review.googlesource.com/c/1326464
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57404}