graphics/pngcheck: Update to 3.0.1

Changes: http://www.libpng.org/pub/png/src/pngcheck-3.0.1.CHANGELOG
PR: 253019
Submitted by: Naram Qashat <cyberbotx@cyberbotx.com> (maintainer)
Approved by: fernape (mentor)
Differential Revision: https://reviews.freebsd.org/D28350