Bump rich from 13.7.0 to 13.8.0 in /backend

Bumps [rich](https://github.com/Textualize/rich) from 13.7.0 to 13.8.0.
- [Release notes](https://github.com/Textualize/rich/releases)
- [Changelog](https://github.com/Textualize/rich/blob/master/CHANGELOG.md)
- [Commits](Textualize/rich@v13.7.0...v13.8.0)

---
updated-dependencies:
- dependency-name: rich
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/requirements.txt

@@ -33,7 +33,7 @@ pyparsing==3.1.1
 python-dotenv==1.0.1
 redis==4.5.4
 requests==2.32.0
-rich==13.7.0
+rich==13.8.0
 six==1.16.0
 sortedcontainers==2.4.0
 toml==0.10.2