Should I disable the HA probe on standby hub before upgrading the primary hub?

Any UIM release

Yes, If the HA probe was left active then it would failover when you start the upgrade. 
Data_engine on the HA hub would then try to write to the DB whilst it is taken offline for the upgrade.
This could lead to lost data.

It is much better to have the robots and secondary hubs queue the data and allow the primary hub to process it after the upgrade.