Assuming that you are talking about the duplicate records in the service now. If you don't want a duplicate record in service now then you can first get the record list using "List Record" and verify whether your enter data if it is already present and according to your business requirement you can discard it or update the existing record.
You can refer to Service Now connector document to know more details of the available action.
If your query was that the duplicate alert was fired by azure monitor then the suggestion would be first verify the condition on which the alert has to be fired and see if that was duplicate. If not then you can always reach out to the monitor team using azure-monitor tags for further assistance.