build(deps-dev): Bump tox from 4.16.0 to 4.21.0

Bumps [tox](https://github.com/tox-dev/tox) from 4.16.0 to 4.21.0.
- [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@4.16.0...4.21.0)

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

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

Author: dependabot[bot]

poetry.lock

@@ -54,7 +54,7 @@ black = "^24.8.0"
 mypy = "^1.11"
 flake8 = "^7.1.1"
 isort = "^5.13.2"
-tox = "^4.16.0"
+tox = "^4.21.0"
 types-requests = "^2.32.0"
 requests-mock = "^1.12.1"
 pytest-cov = "^5.0.0"