Bump mypy from 0.790 to 1.4.0

Bumps [mypy](https://github.com/python/mypy) from 0.790 to 1.4.0.
- [Commits](python/mypy@v0.790...v1.4.0)

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

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