[v10.2.x] DeleteDashboard: Redirect to home after deleting a dashboard

[grafana-delivery-bot]

Backport 8d7314b from #78918

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Fixes #78810

Diagnosis
The useDeleteDashboard was listening to when the result was present in the state.value from useAsyncFn giving a cb to be called onDeleteDashboard. The callback returned by useAsyncFn is used inside another useAsyncFn that hides the modal once the onDeleteDashboard is resolved.

Because onDeleteDashboard is resolved before the next re-render is triggered, the useEffect declared in useDeleteDashboard is never called, so the variables and the replace is never invoked.

Solution
I just simplified this piece of code, since the custom hook useDeleteDashboard is never used. I approached moving everything into a single async callback called when the user clicks confirm. I also removed the duplicated notification to show only one since it did not add much value.