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>