fix: hide connector grants

[j-sneh]

Summary

This is a natural continuation of this issue https://github.com/infrahq/infra/pull/2892, which was also causing a bug with the infra grants list command.

Checklist

• [x] Wrote appropriate unit tests
• [x] Considered security implications of the change
• [x] Updated associated docs where necessary
• [ ] Updated associated configuration where necessary
• [x] Change is backwards compatible if it needs to be (user can upgrade without manual steps?)
• [x] Nothing sensitive logged
• [x] Considered data migrations for smooth upgrades

Related Issues

Resolves #2909