Bump pylint from 2.5.2 to 2.9.6

Bumps [pylint](https://github.com/PyCQA/pylint) from 2.5.2 to 2.9.6.
- [Release notes](https://github.com/PyCQA/pylint/releases)
- [Changelog](https://github.com/PyCQA/pylint/blob/main/ChangeLog)
- [Commits](pylint-dev/pylint@pylint-2.5.2...v2.9.6)

---
updated-dependencies:
- dependency-name: pylint
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements/testing.txt

@@ -4,7 +4,7 @@ coveralls==2.0.0
 flake8==3.9.2
 flake8-isort==2.8.0
 pydocstyle==6.1.1
-pylint==2.5.2
+pylint==2.9.6
 pytest==5.4.2
 pytest-cov==2.12.1
 pytest-timeout==1.3.4