Bump mypy from 0.750 to 0.761 (#24)

Bumps [mypy](https://github.com/python/mypy) from 0.750 to 0.761.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.750...v0.761)

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

Author: dependabot-preview[bot]

requirements.txt

@@ -1,7 +1,7 @@
 entrypoints==0.3
 flake8==3.7.9
 mccabe==0.6.1
-mypy==0.750
+mypy==0.761
 pycodestyle==2.5.0
 pyflakes==2.1.1
 typed-ast==1.4.0