Bump pylint from 2.7.2 to 2.7.4 (#427)

Bumps [pylint](https://github.com/PyCQA/pylint) from 2.7.2 to 2.7.4.
- [Release notes](https://github.com/PyCQA/pylint/releases)
- [Changelog](https://github.com/PyCQA/pylint/blob/master/ChangeLog)
- [Commits](https://github.com/PyCQA/pylint/compare/pylint-2.7.2...pylint-2.7.4)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: Pierre Ståhl <pierre.staahl@gmail.com>

requirements_test.txt

@@ -4,6 +4,6 @@ flake8==3.9.0
 mypy==0.812
 pydocstyle==6.0.0
 cryptography==3.2
-pylint==2.7.2
+pylint==2.7.4
 pylint-strict-informational==0.1
 homeassistant==2021.1.4