Bump tox from 4.20.0 to 4.25.0

Bumps [tox](https://github.com/tox-dev/tox) from 4.20.0 to 4.25.0.
- [Release notes](https://github.com/tox-dev/tox/releases)
- [Changelog](https://github.com/tox-dev/tox/blob/main/docs/changelog.rst)
- [Commits](https://github.com/tox-dev/tox/compare/4.20.0...4.25.0)

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

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

README.md

@@ -232,7 +232,3 @@ xdg-open htmlcov/index.html
 ## License
 
 This project is licensed under the [Apache-2.0](https://github.com/long2ice/fastapi-cache/blob/master/LICENSE) License.
-
-## Sponsor
-
-[![Powered by DartNode](https://dartnode.com/branding/DN-Open-Source-sm.png)](https://dartnode.com "Powered by DartNode - Free VPS for Open Source")