This reverts commit 6ec52d90.

Reason for revert: Caused failure on Chromium android-asan bot. More info in crbug.com/1198565.

Original change's description:
> [wasm] Enable wasm threads by default in V8
>
> Finer grained control of platforms that support threads are
> enforced by chromium.
>
> Bug: chromium:1167733
> Change-Id: Ic34a4950aebf6ba394053b79df97b703af333636
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2810190
> Reviewed-by: Lutz Vahl <vahl@chromium.org>
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#73919}

Bug: chromium:1167733
Change-Id: I8a7740c70c227dea42de5a54bb1cfa07fc139098
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2821704
Auto-Submit: Victor Vianna <victorvianna@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#73939}