Bump @kubernetes/client-node from 0.20.0 to 0.21.0 in /tests/ui (#797)

Bumps [@kubernetes/client-node](https://github.com/kubernetes-client/javascript) from 0.20.0 to 0.21.0.
- [Release notes](https://github.com/kubernetes-client/javascript/releases)
- [Changelog](https://github.com/kubernetes-client/javascript/blob/master/CHANGELOG.md)
- [Commits](https://github.com/kubernetes-client/javascript/commits)

---
updated-dependencies:
- dependency-name: "@kubernetes/client-node"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>