graphics/pngcheck: Update to 3.0.0

• Update to 3.0.0
• Update MASTERSITE to the new upstream
• Pass maintainership to the submitter

Changes: http://www.libpng.org/pub/png/src/pngcheck-3.0.0.CHANGELOG
PR: 252929
Submitted by: Naram Qashat <cyberbotx@cyberbotx.com>