Fix typo from #1354 (#1456)

See: kubernetes-retired/service-catalog#1354 (review)

Signed-off-by: Doug Davis <dug@us.ibm.com>

pkg/apis/servicecatalog/validation/instance.go

@@ -231,7 +231,7 @@ func internalValidateServiceInstanceUpdateAllowed(new *sc.ServiceInstance, old *
 		errors = append(errors, field.Forbidden(field.NewPath("spec"), "Another update for this service instance is in progress"))
 	}
 	if old.Spec.ClusterServicePlanExternalName != new.Spec.ClusterServicePlanExternalName && new.Spec.ClusterServicePlanRef != nil {
-		errors = append(errors, field.Forbidden(field.NewPath("spec").Child("clusterServicePlanRef"), "clusterServicePlanRef must not be present when servicePlanExternalName is being changed"))
+		errors = append(errors, field.Forbidden(field.NewPath("spec").Child("clusterServicePlanRef"), "clusterServicePlanRef must not be present when clusterServicePlanExternalName is being changed"))
 	}
 	return errors
 }