This reverts commit bebb2bdc.

Reason for revert: Breaks GarbageCollectionWithLocalHeap test.
https://ci.chromium.org/p/v8/builders/ci/V8%20Linux%20-%20debug/31107

Original change's description:
> [heap] Allow LocalHeap on the main thread
> 
> This changes the safepoint scope to skip LocalHeap that is active
> for the current thread to avoid deadlocking.
> 
> Bug: v8:10315
> Change-Id: I45e80ae66d0dbbe768107aa9cf0603204c644d9f
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2289983
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#68769}

TBR=ulan@chromium.org,dinfuehr@chromium.org

Change-Id: Ifba8218f9104afed3f2d92258296067f8f424062
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:10315
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2290573Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68770}