Reading --verify_predictable makes me sad, whereas --verify-predictable
makes me happy. This CL introduces more happiness.

R=machenbach@chromium.org

Bug: v8:8834
Change-Id: Id51a75f32e6d5a2f87aed81e058a8b6dff189758
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1550399Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60599}