build(deps): bump tox in /build in the build-dependencies group (#444)

Bumps the build-dependencies group in /build with 1 update: [tox](https://github.com/tox-dev/tox).


Updates `tox` from 4.18.1 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@4.18.1...4.20.0)

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

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

build/build-constraints.txt

@@ -3,5 +3,5 @@ build==1.2.2
 hatchling==1.25.0
 
 # These packages are used used as constraints in workflows
-tox==4.18.1
+tox==4.20.0
 pip-tools==7.4.1