Bump mypy from 1.3.0 to 1.4.0

Bumps [mypy](https://github.com/python/mypy) from 1.3.0 to 1.4.0.
- [Commits](python/mypy@v1.3.0...v1.4.0)

---
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]

poetry.lock

@@ -21,7 +21,7 @@ python = ">=3.7"
 
 [tool.poetry.dev-dependencies]
 asserts = ">=0.8.0,<0.13"
-mypy = "~1.3.0"
+mypy = "~1.4.0"
 
 [tool.black]
 line-length = 79