Bump mypy from 0.930 to 0.931 (#404)

Bumps [mypy](https://github.com/python/mypy) from 0.930 to 0.931.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.930...v0.931)

---
updated-dependencies:
- dependency-name: mypy
  dependency-type: direct:development
  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>

requirements-dev.txt

@@ -4,7 +4,7 @@ coverage==6.2
 docutils==0.17.1
 flake8==4.0.1
 grablib==0.8
-mypy==0.930
+mypy==0.931
 pytest==6.2.5
 pytest-aiohttp==0.3.0
 pytest-cov==3.0.0