[Migrations] Reenable tests fixed by #194151

[gsoldevila]

Summary

• Unskips Failing test: Jest Integration Tests.src/core/server/integration_tests/saved_objects/migrations/group3 - when rolling back to an older version kibana should detect that a later version alias exists, and abort #193756
• Unskips Failing test: Jest Integration Tests.src/core/server/integration_tests/saved_objects/migrations/group3/actions - migration actions reindex & waitForReindexTask resolves left wait_for_task_completion_timeout when the task does not finish within the timeout #166190

Both should be addressed by #194151

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)

[kibana-ci]

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@elasticmachine merge upstream