Bump mypy from 0.942 to 0.991

Bumps [mypy](https://github.com/python/mypy) from 0.942 to 0.991.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.942...v0.991)

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

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

Author: dependabot[bot]

poetry.lock

@@ -48,7 +48,7 @@ python = "^3.7"
 typing_extensions = ">=3.10,<5.0"
 
 [tool.poetry.dev-dependencies]
-mypy = "^0.942"
+mypy = "^0.991"
 
 wemake-python-styleguide = "^0.17"
 flake8-pytest-style = "^1.6"