editors/gobby: Update WWW and MASTER_SITES

For MASTER_SITES, releases.0x539.de redirects directly to GitHub,
so we are downloading static source archive from GitHub now.
For WWW homepage, it's no longer alive, so replace it with up-to-date one.

Reported by: repology
Approved by: osa, vvd (Mentors, implicit)
MFH: 2026Q2