Bump mypy from 0.812 to 0.971

Bumps [mypy](https://github.com/python/mypy) from 0.812 to 0.971.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.812...v0.971)

---
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

@@ -34,7 +34,7 @@ hypothesmith = "^0.1.8"
 
 [tool.poetry.dev-dependencies]
 ipdb = "^0.13.2"
-mypy = "^0.812"
+mypy = "^0.971"
 flake8 = "^3.8.3"
 pytest = "^5.4.3"
 pytest-cov = "^2.10.0"