... since decompression customization for MapWord is already
handled by HeapObject::MapField.

Bug: v8:9353, v8:9183
Change-Id: I009cdbbf8fc7e72029e1b9be54a0f0b73050e738
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1660475
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62188}