Bump cloud_controller_ng

Dependency updates in cloud_controller_ng:

- build(deps-dev): bump undici from 6.20.1 to 6.21.1 in /docs/v3
    PR: cloudfoundry/cloud_controller_ng#4183
    Author: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: ari-wg-gitbot