Revert "Restrict visibility of libpng to current users"

This reverts commit 30284c444a33749e2a4396f9f047b090b7089a34.

Reason for revert: breaks linux builder wayland

https://ci.chromium.org/ui/p/chromium/builders/ci/Linux%20Builder%20(Wayland)/97436/overview

Bug: 433723342
Original change's description:
> Restrict visibility of libpng to current users
>
> No new dependencies should be added on libpng: it is actively being
> migrated to a rust version, and image processing calls should go through
> skia instead of calling libpng directly. This CL enforces that by
> restricting the visibility of libpng targets to the current set of
> users, meaning any new users will require owners approval.
>
> The separate visibility file serves as an easily-auditable record of
> who is currently depending on libpng, and how that changes over time.
>
> Bug: 433723342
> Change-Id: I9e0c94fa1547c1478b849325aa6914e92bfaff9e
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6777532
> Commit-Queue: Devon Loehr <dloehr@google.com>
> Reviewed-by: Chris Blume <cblume@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1491588}

Bug: 433723342
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I6533930f25e230414a1c261d56e603af8e96092d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6783428
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Ben Pastene <bpastene@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Devon Loehr <dloehr@google.com>
Cr-Commit-Position: refs/heads/main@{#1491604}
NOKEYCHECK=True
GitOrigin-RevId: 0281478b61fad578ce7891deea75507aa5cb8650