This reverts commit f124b28d.

Reason for revert: https://logs.chromium.org/logs/v8/buildbucket/cr-buildbucket/8818719400214419665/+/u/Check_-_stress_concurrent_allocation__flakes_/flush-baseline-code

Original change's description:
> [heap] Only start incremental marking when V8 is not in GC VM state.
>
> Bug: v8:12503
> Change-Id: Icda291d9770c46c7fee3c70dd4df97f320b1956a
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3398113
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Hannes Payer <hpayer@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#79623}

Bug: v8:12503
Change-Id: I067b308cfc4511d89144d2bb65a1dba24db62179
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3553104
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Owners-Override: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79629}