Since we switched to C++14 now, we can use {std::make_unique} instead
of our own {base::make_unique} from {template-utils.h}.

R=mstarzinger@chromium.org, yangguo@chromium.org

Bug: v8:9687
No-Try: true
Change-Id: I660eb30038bbb079cee93c7861cd87ccd134f01b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1789300
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63642}