chore(deps): bump mermaid and vuepress-plugin-md-enhance

Removes [mermaid](https://github.com/mermaid-js/mermaid). It's no longer used after updating ancestor dependency [vuepress-plugin-md-enhance](https://github.com/vuepress-theme-hope/vuepress-theme-hope/tree/HEAD/packages/md-enhance). These dependencies need to be updated together.


Removes `mermaid`

Updates `vuepress-plugin-md-enhance` from 1.30.0 to 2.0.0-rc.59
- [Release notes](https://github.com/vuepress-theme-hope/vuepress-theme-hope/releases)
- [Changelog](https://github.com/vuepress-theme-hope/vuepress-theme-hope/blob/main/packages/md-enhance/CHANGELOG.md)
- [Commits](https://github.com/vuepress-theme-hope/vuepress-theme-hope/commits/v2.0.0-rc.59/packages/md-enhance)

---
updated-dependencies:
- dependency-name: mermaid
  dependency-type: indirect
- dependency-name: vuepress-plugin-md-enhance
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]