Bump mypy from 0.971 to 0.981 (#708)

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:production
  update-type: version-update:semver-minor
...

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

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

test-requirements.txt

@@ -4,7 +4,7 @@ pycodestyle==2.9.1
 pydocstyle==6.0.0
 dodgy==0.2.1
 isort==5.10.1
-mypy==0.971
+mypy==0.981
 Werkzeug==1.0.1
 Flask-Testing==0.8.1
 blinker==1.5