Bump mypy from 0.910 to 0.931 (#214)

Bumps [mypy](https://github.com/python/mypy) from 0.910 to 0.931.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.910...v0.931)

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

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

Author: dependabot[bot]

requirements-test.txt

@@ -2,7 +2,7 @@ black==21.7b0
 flake8==4.0.*
 freezegun==1.1.*
 isort==5.10.*
-mypy==0.910
+mypy==0.931
 pytest==6.2.*
 pytest-cov==3.0.*
 pytest-vcr==1.0.*