Revert "Enable unified garbage collections"

This reverts commit a8228cdc699831699180ecd3b327366305c830d2.

Reason for revert: Reverting as we've cycled through the waterfalls and the other flag change on the content layer already got reverted.

Original change's description:
> Enable unified garbage collections
> 
> Enables unified heap garbage collection across V8 and Blink. The GC
> computes a single transitive closure across V8's API boundary before
> starting the separate sweepers.
> 
> Sheriffs: This is a dry-run of the feature and will be reverted after
> cycling through the waterfall and performance bots.
> 
> Bug: 843903
> Change-Id: I0d3e9fc76fa9b116f32d92a234c45afe11120cf9
> Reviewed-on: https://chromium-review.googlesource.com/c/1290869
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Reviewed-by: Kentaro Hara <haraken@chromium.org>
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#605634}

TBR=ulan@chromium.org,haraken@chromium.org,keishi@chromium.org,hpayer@chromium.org,mlippautz@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 843903
Change-Id: I1d1f695431919864cb15dffe0d9b1e4ba85fd3c5
Reviewed-on: https://chromium-review.googlesource.com/c/1329021
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606813}
1 file changed