net-im/mautrix-whatsapp: Update 0.2512.0 => 0.2604.0

Release Notes:
https://mau.fi/blog/2026-04-mautrix-release/

Changelogs:

• https://github.com/mautrix/whatsapp/releases/tag/v0.2601.0
• https://github.com/mautrix/whatsapp/releases/tag/v0.2602.0
• https://github.com/mautrix/whatsapp/releases/tag/v0.2603.0
• https://github.com/mautrix/whatsapp/releases/tag/v0.2604.0

PR: 293289
Reported by: Julian Weigt <juw@posteo.de> (maintainer)
Approved by: osa (mentor)
MFH: 2026Q2