Bump mypy from 1.5.0 to 1.5.1 (#726)

Bumps [mypy](https://github.com/python/mypy) from 1.5.0 to 1.5.1.
- [Commits](python/mypy@v1.5.0...v1.5.1)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

mypy-requirements.txt

@@ -1,4 +1,4 @@
-mypy==1.5.0  # update pyproject.toml as well
+mypy==1.5.1  # update pyproject.toml as well
 black>=19.10b0
 types-pkg_resources
 types-requests