pip prod(deps): bump mypy from 0.931 to 0.940

Bumps [mypy](https://github.com/python/mypy) from 0.931 to 0.940.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.931...v0.940)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements-testing.txt

@@ -8,7 +8,7 @@ pytest-xdist == 2.5.0
 pytest-mock==3.6.1
 pytest-asyncio==0.16.0
 autopep8==1.6.0
-mypy==0.931
+mypy==0.940
 py-spy==0.3.11
 codecov==2.1.12
 tox==3.24.5