This reverts commit 8f1c985c.

Reason for revert: breaks mkgrokdump

Original change's description:
> [heap] Reduce page size to 256KB
> 
> The page size of PPC is kept unchanged because PPC has larger
> physical pages (64KB).
> 
> Bug: chromium:852420
> 
> Change-Id: Ib888ea00a476ff103e00211dbb439186148ef81e
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1481631
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
> Cr-Commit-Position: refs/heads/master@{#60296}

TBR=ulan@chromium.org,hpayer@chromium.org,jyan@ca.ibm.com

Change-Id: I16175bea8845ac5d16dd43af1add4f2d9e94debc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:852420
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1528247Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60298}