Remove the “Switch to GA4 Dashboard View” notification banner

[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 “Switch to GA4 Dashboard View” notification banner (being implemented in #6544) should be removed, as at this point, GA4 will be the only available dashboard view and sites having GA4 connected will be automatically switched over to the GA4 dashboard view.

Along with the BannerNotification, the shouldPromptGA4DashboardView selector in the analytics-4 datastore should also be removed.

Here is the relevant section in the design doc.

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Acceptance criteria

Implementation Brief

Test Coverage

QA Brief

Changelog entry

[nfmohit]

Closing in favour of #6549.