Bump pytest-mypy-plugins from 3.0.0 to 3.1.0

Bumps [pytest-mypy-plugins](https://github.com/TypedDjango/pytest-mypy-plugins) from 3.0.0 to 3.1.0.
- [Release notes](https://github.com/TypedDjango/pytest-mypy-plugins/releases)
- [Changelog](https://github.com/typeddjango/pytest-mypy-plugins/blob/master/CHANGELOG.md)
- [Commits](typeddjango/pytest-mypy-plugins@3.0.0...3.1.0)

---
updated-dependencies:
- dependency-name: pytest-mypy-plugins
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

setup.py

@@ -69,7 +69,7 @@
             "pytest-cov==2.12.1 ; python_version<'3.8'",
             "pytest-cov==4.1.0 ; python_version>='3.8'",
             "pytest-mypy-plugins==1.9.3 ; python_version>='3.6' and python_version<'3.8'",
-            "pytest-mypy-plugins==3.0.0 ; python_version>='3.8'",
+            "pytest-mypy-plugins==3.1.0 ; python_version>='3.8'",
             # Testing utils.
             "colorama==0.4.5 ; python_version<'3.8'",
             "colorama==0.4.6 ; python_version>='3.8'",