kvserver: remove rotten TODO

This TODO was added in 2016 and the surrounding structure of the method
has entirely changed in the intervening period. It doesn't make sense
anymore as we do indeed handle heterogenous sets of replica constraints
now.

Release note: None

pkg/kv/kvserver/allocator.go

@@ -362,7 +362,6 @@ func (a *Allocator) ComputeAction(
 func (a *Allocator) computeAction(
 	ctx context.Context, zone *zonepb.ZoneConfig, voterReplicas []roachpb.ReplicaDescriptor,
 ) (AllocatorAction, float64) {
-	// TODO(mrtracy): Handle non-homogeneous and mismatched attribute sets.
 	have := len(voterReplicas)
 	decommissioningReplicas := a.storePool.decommissioningReplicas(voterReplicas)
 	clusterNodes := a.storePool.ClusterNodeCount()