When we changed FeedbackMetadata to be it's own type instead of a
subtype of FixedArray, we missed this check for valid objects in old
space. This restores the old behavior during verification.

Bug: chromium:862433
Change-Id: Icdb144df4aebc0c6d78a28405c7f53e40b2e1376
Reviewed-on: https://chromium-review.googlesource.com/1134995Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54408}