Bump dompurify and mermaid in /frontend

Bumps [dompurify](https://github.com/cure53/DOMPurify) to 3.2.6 and updates ancestor dependency [mermaid](https://github.com/mermaid-js/mermaid). These dependencies need to be updated together.


Updates `dompurify` from 3.1.6 to 3.2.6
- [Release notes](https://github.com/cure53/DOMPurify/releases)
- [Commits](cure53/DOMPurify@3.1.6...3.2.6)

Updates `mermaid` from 10.9.3 to 11.9.0
- [Release notes](https://github.com/mermaid-js/mermaid/releases)
- [Commits](https://github.com/mermaid-js/mermaid/compare/v10.9.3...mermaid@11.9.0)

---
updated-dependencies:
- dependency-name: dompurify
  dependency-version: 3.2.6
  dependency-type: indirect
- dependency-name: mermaid
  dependency-version: 11.9.0
  dependency-type: direct:production
...

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Author: dependabot[bot]