Bump pylint-django from 2.5.5 to 2.6.1

Bumps [pylint-django](https://github.com/pylint-dev/pylint-django) from 2.5.5 to 2.6.1.
- [Release notes](https://github.com/pylint-dev/pylint-django/releases)
- [Changelog](https://github.com/pylint-dev/pylint-django/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pylint-dev/pylint-django/commits/v2.6.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements/readthedocs.txt

@@ -11,6 +11,6 @@ factory_boy
 mock
 pydot
 # linting tools
-pylint-django==2.5.5
+pylint-django==2.6.1
 twine
 pyOpenSSL