Revert of [heap] Fix Sweeper::IsSweepingCompleted (patchset #1 id:1 of https://codereview.chromium.org/2047013004/ )

Reason for revert:
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20TSAN/builds/10009

Original issue's description:
> [heap] Fix Sweeper::IsSweepingCompleted
>
> R=ulan@chromium.org
>
> Committed: https://crrev.com/b4475fff4fe1c423a3c8c3b072e09becd6b2f8ed
> Cr-Commit-Position: refs/heads/master@{#36845}

TBR=ulan@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2053623002
Cr-Commit-Position: refs/heads/master@{#36850}