Bump @testing-library/react in /src/Elastic.Documentation.Site

Bumps [@testing-library/react](https://github.com/testing-library/react-testing-library) from 14.3.1 to 16.3.0.
- [Release notes](https://github.com/testing-library/react-testing-library/releases)
- [Changelog](https://github.com/testing-library/react-testing-library/blob/main/CHANGELOG.md)
- [Commits](testing-library/react-testing-library@v14.3.1...v16.3.0)

---
updated-dependencies:
- dependency-name: "@testing-library/react"
  dependency-version: 16.3.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]