097fae groups.d/251.native_packages_lib.group: libpng: bump to v1.6.40

Authored and Committed by Redfoxmoon a year ago
    groups.d/251.native_packages_lib.group: libpng: bump to v1.6.40
    
    Signed-off-by: Ørjan Malde <red@foxi.me>