build(deps-dev): bump darker[flynt,isort] from 1.6.1 to 2.0.0

Bumps [darker[flynt,isort]](https://github.com/akaihola/darker) from 1.6.1 to 2.0.0.
- [Release notes](https://github.com/akaihola/darker/releases)
- [Changelog](https://github.com/akaihola/darker/blob/master/CHANGES.rst)
- [Commits](akaihola/darker@1.6.1...v2.0.0)

---
updated-dependencies:
- dependency-name: darker[flynt,isort]
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements-dev.txt

@@ -1,4 +1,4 @@
-darker[flynt,isort] == 1.6.1
+darker[flynt,isort] == 2.0.0
 freezegun == 1.1.0
 mypy == 1.0.0
 pre-commit == 3.3.3