Prevent rendering Key Metrics if setup not completed

[jimmymadon]

Bug Description

@aaemnnosttv: This isn't a particularly realistic scenario.

Steps to reproduce

1. Setup and enable the KMW widget.
2. In the database, delete the googlesitekit_key_metrics_setup_completed_by
3. Refresh the dashboard and the key metrics still render alongside the Key metrs Setup CTA Banner.

Screenshots

Additional Context

• PHP Version:
• OS: [e.g. iOS]
• Browser: [e.g. chrome, safari]
• Plugin Version: [e.g. 22]
• Device: [e.g. iPhone6]

---

Do not alter or remove anything below. The following sections will be managed by moderators only.

Acceptance criteria

Implementation Brief

Test Coverage

QA Brief

Changelog entry