Bump skaut/wordpress-stubs from 2.8.1 to 2.9.0

Bumps [skaut/wordpress-stubs](https://github.com/skaut/wordpress-stubs) from 2.8.1 to 2.9.0.
- [Release notes](https://github.com/skaut/wordpress-stubs/releases)
- [Commits](skaut/wordpress-stubs@2.8.1...2.9.0)

---
updated-dependencies:
- dependency-name: skaut/wordpress-stubs
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>