This was wrong because ObjectBoilerplateDescription is a subclass of
FixedArray. The wrong order didn't cause problems because we explicitly
call the ObjectBoilerplateDescription constructor in the places that
matter.

Bug: v8:7790
Change-Id: I63b6b8741472862d2b1b9b843d7aa2490c620f87
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2335180
Commit-Queue: Georg Neis <neis@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69219}