Update isGA4DashboardView selector

[nfmohit]

Feature Description

Note: This shall only be implemented to be released as a part of the Site Kit update/release going right after UA has a zero-data state.

As a part of the Site Kit update/release going right after UA has a zero-data state, the isGA4DashboardView selector (being implemented in #6541) should be updated so that if GA4 is connected, it should unconditionally return true. Since Site Kit will automatically switch to the GA4 dashboard view at this point, this selector returning true will not require us to change the logic immediately and give us a generous amount of time to remove the selector and the UA module overall.

Here is the relevant part of the design doc.

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Acceptance criteria

Implementation Brief

Test Coverage

QA Brief

Changelog entry

[nfmohit]

Closing in favour of #6549.