Remove mocked methods from dashboard spec

What does this MR do?

Remove mocked methods from dashboard spec.

As part of #215472 (closed) (see comment !30476 (comment 331944870)) some Vuex actions should be refactored, this small change sets up specs for such refactoring.

In order to ensure that the Vuex store wiring is correct, specs should not replace methods like fetchData(). This change mock the store dispatch instead.

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Does this MR meet the acceptance criteria?

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