build(deps): bump mistune in /docker/sane-doc-reports (#36112)

Bumps [mistune](https://github.com/lepture/mistune) from 3.1.1 to 3.1.2.
- [Release notes](https://github.com/lepture/mistune/releases)
- [Changelog](https://github.com/lepture/mistune/blob/master/docs/changes.rst)
- [Commits](lepture/mistune@v3.1.1...v3.1.2)

---
updated-dependencies:
- dependency-name: mistune
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>