Bump mypy from 0.942 to 0.971

Bumps [mypy](https://github.com/python/mypy) from 0.942 to 0.971.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.942...v0.971)

---
updated-dependencies:
- dependency-name: mypy
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

dev-requirements.txt

@@ -11,7 +11,7 @@ flake8
 flaky
 freezegun==0.3.12
 ipdb
-mypy==0.942
+mypy==0.971
 pip-tools
 pre-commit
 pytest