Add to libpng's visibility list

One more bot that we missed when constructing the initial list

Bug: 433723342
Change-Id: I3a24b2931639d29c201ad1402a7286ba262b0ac3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6801935
Auto-Submit: Devon Loehr <dloehr@google.com>
Reviewed-by: Chris Blume <cblume@chromium.org>
Commit-Queue: Chris Blume <cblume@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1494355}
NOKEYCHECK=True
GitOrigin-RevId: 697d6dd1708f1e67f7ae20ae465a59a462bde472