Bump mypy from 0.750 to 0.760 (#215)

Bumps [mypy](https://github.com/python/mypy) from 0.750 to 0.760.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.750...v0.760)

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

Author: dependabot-preview[bot]

poetry.lock

@@ -47,7 +47,7 @@ python = "^3.6"
 typing-extensions = "^3.7"
 
 [tool.poetry.dev-dependencies]
-mypy = "^0.750"
+mypy = "^0.760"
 wemake-python-styleguide = "^0.13.3"
 flake8-pytest = "^1.3"
 flake8-pytest-style = "^0.1.3"