Bump mypy from 0.910 to 0.920 (#384)

Bumps [mypy](https://github.com/python/mypy) from 0.910 to 0.920.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.910...v0.920)

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

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

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

requirements-dev.txt

@@ -4,7 +4,7 @@ bandit==1.7.1
 coverage==6.2
 docutils==0.18.1
 flake8==4.0.1
-mypy==0.910
+mypy==0.920
 pyroma==3.2
 pytest-cov==3.0.0
 pytest==6.2.5