Bump platformdirs from 2.5.4 to 2.6.0

Bumps [platformdirs](https://github.com/platformdirs/platformdirs) from 2.5.4 to 2.6.0.
- [Release notes](https://github.com/platformdirs/platformdirs/releases)
- [Changelog](https://github.com/platformdirs/platformdirs/blob/main/CHANGES.rst)
- [Commits](tox-dev/platformdirs@2.5.4...2.6.0)

---
updated-dependencies:
- dependency-name: platformdirs
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

test-requirements.txt

@@ -77,7 +77,7 @@ pexpect==4.8.0
     # via ipython
 pickleshare==0.7.5
     # via ipython
-platformdirs==2.5.4
+platformdirs==2.6.0
     # via
     #   black
     #   pylint