Bump mypy from 0.790 to 0.961

Bumps [mypy](https://github.com/python/mypy) from 0.790 to 0.961.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.790...v0.961)

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

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

Author: dependabot[bot]

requirements-dev.txt

@@ -3,7 +3,7 @@ flake8==3.8.*
 isort[requirements]==5.7.*
 mongomock==3.22.*
 moto==1.3.*
-mypy==0.790
+mypy==0.961
 pytest==6.2.*
 pytest-cov==2.11.*
 pytest-mock==3.5.*