Dashboard Sharing setup is blocked when PageSpeed Insights module is disconnected

## Bug Description

Dashboard Sharing setup is blocked when the PageSpeed Insights (PSI) module is disconnected.

When all other Site Kit modules are connected, disconnecting only the PageSpeed Insights module causes Dashboard Sharing setup to fail. The Apply button remains disabled, preventing users from completing the Dashboard Sharing configuration.

Dashboard Sharing should not depend on the PSI module connection, as PSI is not required for sharing the dashboard.

## Steps to reproduce

1. Set up Site Kit and connect all available modules.
2. Disconnect only the PageSpeed Insights (PSI) module.
3. Navigate to Site Kit → Settings → Dashboard Sharing.
4. Configure Dashboard Sharing and try to apply the changes.

## Screenshots

https://github.com/user-attachments/assets/ca80c787-b432-4c49-b744-6b85375d01e8

## Additional Context

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

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## Acceptance criteria

*

## Implementation Brief

* [ ]

### Test Coverage

*

## QA Brief

*

## Changelog entry

*

Start in the Dashboard Sharing settings flow and reproduce the issue with all modules connected, then with only PageSpeed Insights disconnected. Trace why the Apply button remains disabled and verify that Dashboard Sharing can be configured and applied without PSI; add regression coverage if the existing settings tests cover this flow.

Written by the indexing model from the issue text.