bug: workspace plugin run against older kcp version produces error output

[ntnn]

Describe the bug

See #4070 (reply in thread)

Likely the workspace plugin is trying to list v1alpha2 and that error is printed to the user.

Steps To Reproduce

See #4070 (reply in thread)

Expected Behaviour

The error should not be visible to the user - we can reasonably expect not all API versions to be available.

Additional Context

No response