As part of https://github.com/camunda/camunda-optimize/pull/1948, we stopped using the activityInstanceId of FlowNodeEvents.

When we create that for running and completed activity imports, we actually assign the value of the parentActivityInstanceId from the historic engine event, so the value is not unique and not helpful (confusing even). We should remove it from the FlowNodeEventDto to avoid it being used in the wrong way again, as in the linked ticket.

ATs:

• We no longer store the activityInstanceId of a FlowNodeEventDto (this is already mapped as the id property)