Bump mypy from 0.971 to 0.981 (#351)

Bumps [mypy](https://github.com/python/mypy) from 0.971 to 0.981.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.971...v0.981)

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

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

requirements_dev.txt

@@ -3,7 +3,7 @@
 black==22.8.0
 flake8==5.0.4
 isort==5.10.1
-mypy==0.971
+mypy==0.981
 pillow==9.2.0
 pip-tools==6.8.0
 pre-commit==2.20.0