Update tox requirement from <4.0.0,>=3.21.0 to >=3.21.0,<5.0.0 (#690)

Updates the requirements on [tox](https://github.com/tox-dev/tox) to permit the latest version.
- [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@3.21.0...4.0.2)

---
updated-dependencies:
- dependency-name: tox
  dependency-type: direct:development
...

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

requirements/dev.txt

@@ -19,7 +19,7 @@ ipywidgets>=7.6.5, <9.0.0 # for notebook tests
 alibi-testing @ git+https://github.com/SeldonIO/alibi-testing@master#egg=alibi-testing # pre-trained models for testing
 # other
 pre-commit>=1.20.0, <3.0.0
-tox>=3.21.0, <4.0.0 # used to generate licence info via `make licenses`
+tox>=3.21.0, <5.0.0 # used to generate licence info via `make licenses`
 twine>3.2.0, <4.0.0  # 4.x causes deps clashes with testing/requirements.txt, as requires rich>=12.0.0 -> requires typing-extensions>=4.0.0 -> too high for spacy and thinc!
 packaging>=19.0, <23.0 # Used to check scipy version for CVMDrift test. Can be removed once python 3.6 support dropped (and scipy lower bound >=1.7.0).
 codecov>=2.0.15, <3.0.0