Fix invalid Windows header include. Was detected from the recent loader roll. Bug: angleproject:6476 Change-Id: Ifebf6d642727a92b7daff018723b7bf8f227ed6f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3198742 Reviewed-by: Ian Elliott <ianelliott@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>