chore(deps): update lunr requirement from >=0.5.8 to >=0.8.0

Updates the requirements on [lunr](https://github.com/yeraydiazdiaz/lunr.py) to permit the latest version.
- [Changelog](https://github.com/yeraydiazdiaz/lunr.py/blob/master/CHANGELOG.md)
- [Commits](yeraydiazdiaz/lunr.py@0.5.8...0.8.0)

---
updated-dependencies:
- dependency-name: lunr
  dependency-version: 0.8.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -9,7 +9,7 @@ idna>=2.10
 Jinja2>=3.1.5
 joblib>=1.5.3
 livereload>=2.6.3
-lunr>=0.5.8
+lunr>=0.8.0
 Markdown>=3.3.4
 MarkupSafe>=2.0.1
 mkdocs>=1.1.2