Bump tox from 3.25.1 to 3.26.0 (#403)

Bumps [tox](https://github.com/tox-dev/tox) from 3.25.1 to 3.26.0.
- [Release notes](https://github.com/tox-dev/tox/releases)
- [Changelog](https://github.com/tox-dev/tox/blob/master/docs/changelog.rst)
- [Commits](tox-dev/tox@3.25.1...3.26.0)

---
updated-dependencies:
- dependency-name: tox
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements_dev.txt

@@ -3,6 +3,6 @@
 -r requirements_mypy.txt
 -r requirements_pypi.txt
 -r requirements_test.txt
-tox==3.25.1
+tox==3.26.0
 
 -e .