... from Object to HeapObject, as they are never Smis.

Change-Id: I4cbe12985091ed1b1e94dab2803a977ae3e25224
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1541104
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60543}