Bump mypy from 0.730 to 0.740

Bumps [mypy](https://github.com/python/mypy) from 0.730 to 0.740.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.730...v0.740)

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

Author: dependabot-preview[bot]

setup.py

@@ -4,7 +4,7 @@
 EXTRAS_REQUIRE = {
     "tests": ["pytest", "pytz", "simplejson"],
     "lint": [
-        "mypy==0.730",
+        "mypy==0.740",
         "flake8==3.7.8",
         "flake8-bugbear==19.8.0",
         "pre-commit~=1.17",