net-im/mautrix-whatsapp: Update 0.2604.0 => 0.2606.0

Added sample config that is created by running mautrix-whatsapp -e
and also commenting out logging to files since this is handled by
daemon(8) when running as a service.

While here, require Go 1.26+ otherwise it gets downloaded manually.

Release Notes:

• https://mau.fi/blog/2026-05-mautrix-release/
• https://mau.fi/blog/2026-06-mautrix-release/

Changelogs:

• https://github.com/mautrix/whatsapp/releases/v0.2605.0
• https://github.com/mautrix/whatsapp/releases/v0.2606.0

PR: 295337
MFH: 2026Q2
Approved by: osa, vvd (Mentors, implicit)

(cherry picked from commit 31af87cee4d53498ebe5fca9787b2d681fea804a)