This reverts commit 49bd7f50.

Reason for revert: breaks nonintl build since the added string is inside wrong ifdefs

Original change's description:
> [js weak refs] Add WeakCell.clear()
> 
> BUG=v8:8179
> 
> Change-Id: Ic0d9af273a8a92177bf60e4be0dd5bddaf31868c
> Reviewed-on: https://chromium-review.googlesource.com/c/1292058
> Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Commit-Queue: Marja Hölttä <marja@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#56853}

TBR=marja@chromium.org,hpayer@chromium.org,gsathya@chromium.org

Change-Id: I7d6831cfd8a5263ee327c2a80274d1cd10dd65cc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:8179
Reviewed-on: https://chromium-review.googlesource.com/c/1293573Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56855}