Bump pylint from 2.5.3 to 2.6.0 (#524)

Author: dependabot[bot]

requirements/requirements_dev.txt

@@ -9,7 +9,7 @@ flake8-bugbear==20.1.4
 hypothesis==4.53.1
 placebo==0.9.0
 pre-commit==2.6.0
-pylint==2.5.3
+pylint==2.6.0
 pytest==6.1.1
 pytest-black==0.3.10
 pytest-cov==2.10.0