Improve UX/UI on Dashboard Sharing when an admin disconnects Site Kit

## Bug Description

There's a weird UX/UI experience in a specific scenario on a site with two admin users for dashboard sharing.

`Admin 1` connects Site Kit and gives permission to modules in the dashboard sharing settings modal. `Admin 2` logs in to his WordPress account but does not connect his Google account. Instead they go to the shared dashboard. Later on `Admin 1 ` disconnects Site Kit. Then `Admin 2` logs back in and when they go to the Site Kit Dashboard, lots of data unavailable messages appear.

I am wondering if we can improve the UX/UI in this scenario.

Maybe we should show a reconnect button so that they can reconnect with their Google account.

You can connect your Google account by going to the View only menu but it isn't obvious.

It's unlikely this scenario would happen often but could create support tickets so feel it needs improving.


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## Acceptance criteria

* The view-only dashboard should show a single, clear component when Site Kit has been disconnected by a site admin.
* If the current user is an administrator they can re-connect Site Kit via a CTA.

## Implementation Brief

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### Test Coverage

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## QA Brief

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## Changelog entry

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