After https://crrev.com/c/3315446 we allocate the memory protection key
unconditionally, so the method is redundant.

R=ahaas@chromium.org

Bug: v8:11974
Change-Id: I205a0cda86dfaf394c68788a662241d76a3f8510
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3347562Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78412}