build(deps-dev): bump pestphp/pest from 2.12.2 to 2.21.0

Bumps [pestphp/pest](https://github.com/pestphp/pest) from 2.12.2 to 2.21.0.
- [Release notes](https://github.com/pestphp/pest/releases)
- [Changelog](https://github.com/pestphp/pest/blob/2.x/RELEASE.md)
- [Commits](pestphp/pest@v2.12.2...v2.21.0)

---
updated-dependencies:
- dependency-name: pestphp/pest
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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