Bump mypy from 0.750 to 0.760 (#1477)

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] <[email protected]>

Author: dependabot-preview[bot]

setup.py

@@ -4,7 +4,7 @@
 EXTRAS_REQUIRE = {
     "tests": ["pytest", "pytz", "simplejson"],
     "lint": [
-        "mypy==0.750",
+        "mypy==0.760",
         "flake8==3.7.9",
         "flake8-bugbear==19.8.0",
         "pre-commit~=1.20",