Bump mypy from 0.812 to 0.902 (#290)

Bumps [mypy](https://github.com/python/mypy) from 0.812 to 0.902.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.812...v0.902)

---
updated-dependencies:
- dependency-name: mypy
  dependency-type: direct:production
  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-testing.txt

@@ -5,6 +5,6 @@ pytest-cov==2.12.1
 pytest-mock==3.6.1
 pycodestyle==2.7.0
 flake8==3.9.2
-mypy==0.812
+mypy==0.902
 mypy-extensions==0.4.3
 typing-extensions==3.10.0.0