Add Data Label to Instance StatefulSet

This commit adds the appropriate 'data' Label to the PostgresCluster
Instance's StatefulSet, in keeping with the labeling pattern used
for the pgBackRest Repo StatefulSet and the pgAdmin Deployment.

Author: tjmoore4

internal/controller/postgrescluster/instance.go

@@ -1115,6 +1115,7 @@ func generateInstanceStatefulSetIntent(_ context.Context,
 			naming.LabelCluster:     cluster.Name,
 			naming.LabelInstanceSet: spec.Name,
 			naming.LabelInstance:    sts.Name,
+			naming.LabelData:        naming.DataPostgres,
 		})
 	sts.Spec.Selector = &metav1.LabelSelector{
 		MatchLabels: map[string]string{