build(deps): bump mermaid from 11.12.2 to 11.15.0 in /ui-tests

Bumps [mermaid](https://github.com/mermaid-js/mermaid) from 11.12.2 to 11.15.0.
- [Release notes](https://github.com/mermaid-js/mermaid/releases)
- [Commits](https://github.com/mermaid-js/mermaid/compare/mermaid@11.12.2...mermaid@11.15.0)

---
updated-dependencies:
- dependency-name: mermaid
  dependency-version: 11.15.0
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]