Bump pipenv from 2020.11.15 to 2022.1.8 in /backend (#45)

Bumps [pipenv](/~https://github.com/pypa/pipenv) from 2020.11.15 to 2022.1.8.
- [Release notes](/~https://github.com/pypa/pipenv/releases)
- [Changelog](/~https://github.com/pypa/pipenv/blob/main/CHANGELOG.rst)
- [Commits](pypa/pipenv@v2020.11.15...v2022.1.8)

---
updated-dependencies:
- dependency-name: pipenv
  dependency-type: direct:production
...

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