Drive-by: cleanup PersistentTest and MarkerTest

Bug: chromium:1056170
Change-Id: I85d674cda7d580e8cd7be807791ba883b0f7a111
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2827898
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73979}