Gcov builds such as
https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20-%20gcov%20coverage/18276
are failing because they can't find std::copy_if. Including the right
header fixes it.

Change-Id: I3f0e3fabfe1b32cc4492aee64d2b9f23fa4afdcb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1600431Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61364}