This reverts commit 90405027.

Reason for revert: Flaky msan:
https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20arm64%20-%20sim%20-%20MSAN/builds/18432

Original change's description:
> [heap] Tune incremental marking step size.
> 
> The main thread now can reduce marking step size if concurrent marking
> tasks are making progress and the bailout worklist is empty.
> 
> Bug: chromium:694255
> Change-Id: I2f58530f184c03667ab3a170a1f6309929645c7c
> Reviewed-on: https://chromium-review.googlesource.com/735859
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49671}

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

Change-Id: Ic10ee9bae51b2b4b78d87c83c67b1307d0c36012
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:694255
Reviewed-on: https://chromium-review.googlesource.com/794190Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49680}