Disable bytecode flushing for test as it messes up lazy source
positions and the flags aren't representative anyway.

Bug: v8:8510
Change-Id: I6d5bc8dcd174a9bfc48f682518e6c62d79acb691
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1658152
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Auto-Submit: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62155}