We're phasing out the -HA SKUs, which were only offered on the lower end appliances anyway.
For older appliances we sell, we'll continue to offer it where we had previously.
The new appliances we've introduced recently don't have these SKUs.
Note that -HA SKUs were never required to deploy a cluster but it did offer a slight discount for the second (or additional appliance.
Also, appliances that have an -HA SKU can only be deployed in a cluster, which can cause issues if you redeploy the appliance down the road.