Otherwise std::allocator is used and there is no conversion.

Bug: chromium:819294
Change-Id: Ic93e75a3facef96dc901dda29a6be3b4539b68e7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3492523Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Stephan Hartmann <stha09@googlemail.com>
Cr-Commit-Position: refs/heads/main@{#79302}