Changing coverage mode generated different bytecode in some cases.
Hence it is not safe to flush bytecode once we toggle coverage mode.

Bug: chromium:1147917
Change-Id: I9e640aeaec664d3d4a4aaedf809c568e9ad924fc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2615020
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71985}