It can happen that the {value} handle initially (when we stored its
contents into the property cell) contained a ThinString but was
subsequently patched by the scavenger to hold the InternalizedString
directly.

Bug: v8:11675
Change-Id: Ia3e5fed5bd28313b6fd2031eee0658ac4136a7ca
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2843350Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74083}