How to manually close DuplicateCIs Tasks so it won't show up in CMDB Health Dashboard.
1. Analyse de-dup task and determine which CI should remain active and which need to be deleted / inactive (Doc link: https://support.servicenow.com/kb_view.do?sys_kb_id=c461ed2adb2fc30068c1fb651f961900)
2. Close the task.
3. Set the task to Inactive by uncheck the "Active" checkbox.
4. Wait for next CMDB Dashboard job to complete.
From CMDB Dashboard, click the record class that need to be closed:
it will redirect to "reconcile_duplicate_task" table.