Bump tox from 4.19.0 to 4.20.0

Bumps [tox](https://github.com/tox-dev/tox) from 4.19.0 to 4.20.0.
- [Release notes](https://github.com/tox-dev/tox/releases)
- [Changelog](https://github.com/tox-dev/tox/blob/main/docs/changelog.rst)
- [Commits](tox-dev/tox@4.19.0...4.20.0)

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

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

requirements-test.txt

@@ -1,3 +1,3 @@
-tox==4.19.0
+tox==4.20.0
 coverage==7.6.1
 ruff==0.6.5