chore(deps): update dependency tox to v4.31.0 (#868)

This PR contains the following updates:

| Package | Change | Age | Confidence |
|---|---|---|---|
| [tox](https://redirect.github.com/tox-dev/tox)
([changelog](https://tox.wiki/en/latest/changelog.html)) | `==4.30.3` ->
`==4.31.0` |
[![age](https://developer.mend.io/api/mc/badges/age/pypi/tox/4.31.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/tox/4.30.3/4.31.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>tox-dev/tox (tox)</summary>

###
[`v4.31.0`](https://redirect.github.com/tox-dev/tox/releases/tag/4.31.0)

[Compare
Source](https://redirect.github.com/tox-dev/tox/compare/4.30.3...4.31.0)

<!-- Release notes generated using configuration in .github/release.yml
at 4.31.0 -->

#### What's Changed

- Address a type-conversion noted during doc builds by
[@&#8203;kurtmckee](https://redirect.github.com/kurtmckee) in
[#&#8203;3623](https://redirect.github.com/tox-dev/tox/pull/3623)
- Add 3.14, drop 3.9 and support | union style by
[@&#8203;gaborbernat](https://redirect.github.com/gaborbernat) in
[#&#8203;3624](https://redirect.github.com/tox-dev/tox/pull/3624)

**Full Changelog**:
<tox-dev/tox@4.30.3...4.31.0>

</details>

---

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rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

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---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Motoi Okuzono <motoi.okuzono+github@gmail.com>

Author: renovate[bot]

requirements-dev.txt

@@ -1,6 +1,7 @@
 -r requirements.txt
 -r requirements-test.txt
-tox==4.30.3
+tox==4.31.0 ; python_version >= "3.10"
+tox==4.30.3 ; python_version < "3.10"
 wheel==0.46.1
 Sphinx==7.4.7
 sphinx-rtd-theme==3.0.2