There is a proposal to make this defined behaviour, so remove the
deprecation comment for now.

R=jkummerow@chromium.org

Bug: v8:3770
Change-Id: Iff50ec544473bed844c586ed242bd062e8d530d8
Reviewed-on: https://chromium-review.googlesource.com/1160238Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54882}