Bump tox from 3.25.1 to 3.26.0 in /requirements

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:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements/tox.txt

@@ -1,3 +1,3 @@
 -r ./coverage.txt
-tox==3.25.1
+tox==3.26.0
 tox-gh-actions==2.10.0