Bump immutabledict from 4.0.0 to 4.1.0 in /extra_requirements (#490)

Bumps [immutabledict](https://github.com/corenting/immutabledict) from 4.0.0 to 4.1.0.
- [Release notes](https://github.com/corenting/immutabledict/releases)
- [Changelog](https://github.com/corenting/immutabledict/blob/master/CHANGELOG.md)
- [Commits](corenting/immutabledict@v4.0.0...v4.1.0)

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

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