Removes the static protector values from isolate now that they are
no longer needed.

This is the final cl in the migration effort.

Bug: v8:9463
Change-Id: I2127ef6c8a0cdaf0ccf28aed12539335ef985704
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1827455Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Joshua Litt <joshualitt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64068}