SL's VisitSpeculativeIntegerAdditiveOp was setting Signed32 as
restriction type even when relying on a Word32 truncation in order to
skip the overflow check. This is not sound.

Bug: chromium:1150649
Change-Id: I3113a2102c62d6ecef342c98d25daf31431c01ed
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2557498Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71364}