Bump @wdio/local-runner from 8.20.5 to 8.21.0 in /testing

Bumps [@wdio/local-runner](https://github.com/webdriverio/webdriverio/tree/HEAD/packages/wdio-local-runner) from 8.20.5 to 8.21.0.
- [Release notes](https://github.com/webdriverio/webdriverio/releases)
- [Changelog](https://github.com/webdriverio/webdriverio/blob/main/CHANGELOG.md)
- [Commits](https://github.com/webdriverio/webdriverio/commits/v8.21.0/packages/wdio-local-runner)

---
updated-dependencies:
- dependency-name: "@wdio/local-runner"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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