As of v8:6536, we no longer have to mark builtins explicitly.

Also remove test whitelist for promise finally
builtins.

Bug: v8:6088, v8:5967
Change-Id: I7f98dfe7708678653e944ac76ba9938205490b16
Reviewed-on: https://chromium-review.googlesource.com/654067
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47896}