Drive-by fix IWYU for instruction-scheduler-ia32.cc.

Bug: v8:11217,v8:7490
Change-Id: I7ae4fdaf3c48274e9421e6b31897ad0ea1464876
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2585254Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71750}