The check was accidentally done only when a stress-flag was enabled.
Moreover, the check is actually unnecessary because the code will deopt
itself once it gets run.

Also add a DCHECK that these invalidations can only happen due to
pretenuring changes.

Bug: v8:8520
Change-Id: Ibb008f93e9e417d2f88cd5fd8fd1380db88bbb85
Reviewed-on: https://chromium-review.googlesource.com/c/1384304Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58395}