Bump pipenv from 2023.7.23 to 2023.9.8 in /requirements

Bumps [pipenv](https://github.com/pypa/pipenv) from 2023.7.23 to 2023.9.8.
- [Release notes](https://github.com/pypa/pipenv/releases)
- [Changelog](https://github.com/pypa/pipenv/blob/main/CHANGELOG.md)
- [Commits](pypa/pipenv@v2023.7.23...v2023.9.8)

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

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

requirements/pipenv.txt

@@ -1 +1 @@
-pipenv==2023.7.23
+pipenv==2023.9.8