This reverts commit e5d568f4.

Reason for revert: Compile error: https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Fuchsia%20-%20builder/9825/overview

Original change's description:
> heap: Implement DiscardSystemPages for Fuchsia
>
> Bug: v8:12050
> Change-Id: I9fa5c0d38f277e363befbdaecaaedd4ee55bfb07
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3071208
> Reviewed-by: Wez <wez@chromium.org>
> Commit-Queue: Omer Katz <omerkatz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#76160}

Bug: v8:12050
Change-Id: I2abdadc4b47656074aa49323f9896695ab5642df
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3080576
Auto-Submit: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#76161}