This reverts commit 1ec2ca26.

Reason for revert: Preparing for re-enabling pointer compression.

Original change's description:
> [ptr-compr] Temporarily enable double fields unboxing
>
> We are not shipping ptr-compr in M79 on x64 because chromium:1009439
> blocks 31-bit Smis on 64-bit architectures, so these's no point in
> disabling double fields unboxing.
>
> This CL will be reverted after the M79 branch point.
>
> Bug: v8:9799, chromium:1009439
> Change-Id: I28d0013d3ab06ce41d5028ba4f66c9b249de52d7
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1862556
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Commit-Queue: Igor Sheludko <ishell@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#64288}

Bug: v8:9799, chromium:1009439
Change-Id: I18e22422725777ad8bfbb19243158228f3559c32
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1919320Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64990}