This reverts commit e2408c25.

Reason for revert: https://ci.chromium.org/p/v8/builders/ci/V8%20Mac64/36733?1

Original change's description:
> [regexp] Protect against reentrant RegExpStack use
>
> Irregexp, and in particular the RegExpStack, are not reentrant.
> Explicitly guard against reentrancy.
>
> Bug: chromium:1125934
> Change-Id: I0fc295f6986a89221982e6a2ccefed46193974f6
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2460820
> Commit-Queue: Yang Guo <yangguo@chromium.org>
> Auto-Submit: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#70436}

TBR=yangguo@chromium.org,jgruber@chromium.org

Change-Id: I7b51659d21fe2d49ff343f4de0f6bb9720281b86
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:1125934
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2465822Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70437}