net/{,py-}scamper: Update 20260420 => 20260902

Changelogs:

• https://mailman.caida.org/pipermail/scamper-announce/2026-July/000063.html
• https://mailman.caida.org/pipermail/scamper-announce/2026-September/000064.html

PR: 298131
Reported by: Matthew Luckie <mjl@luckie.org.nz> (maintainer)
Approved by: osa, vvd (Mentors, implicit)