This reverts commit d0f7c6a8.

Reason for revert: Causing flaky tests https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Mac64%20-%20debug/31929/overview

Original change's description:
> Reland "[wasm-simd][arm] Prototype i8x16.popcnt"
>
> This is a reland of e2aa734a
>
> The original change was speculatively reverted in
> https://crrev.com/c/2568925 but seems unrelated to the flakey
> test failures (which are on x64).
>
> Original change's description:
> > [wasm-simd][arm] Prototype i8x16.popcnt
> >
> > Bug: v8:11002
> > Change-Id: Ib97e51ed52249a1af7a4b879396b70a016991719
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2567534
> > Commit-Queue: Zhi An Ng <zhin@chromium.org>
> > Reviewed-by: Bill Budge <bbudge@chromium.org>
> > Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#71552}
>
> Bug: v8:11002
> Change-Id: I714918e2640d27d29953f940e3bedeb9ea2f8a08
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2567243
> Commit-Queue: Zhi An Ng <zhin@chromium.org>
> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> Reviewed-by: Bill Budge <bbudge@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#71585}

TBR=bbudge@chromium.org,jkummerow@chromium.org,v8-arm-ports@googlegroups.com,zhin@chromium.org

Change-Id: Ib8454a4c20937495c2b83b7ceb3ad594b1b9e7e5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:11002
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2569559Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71586}