Objects that have kind() kBackgroundSerializedHeapObject also should
have been serialized.

Change-Id: I2a3f17df61477409e94b8858e720e1a2ec720091
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2835709
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Auto-Submit: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74037}