www/threema-web: update 2.4.2 to 2.5.0

• https://github.com/threema-ch/threema-web/blob/v2.5.0/CHANGELOG.md
• https://github.com/threema-ch/threema-web/compare/v2.4.2...v2.5.0

PR: 268391
Submitted by: Ralf van der Enden <tremere % cainites.net>