Remove cluster update validation for primary to secondary (GoogleCloudPlatform#10588)

Author: 199201shubhamsahu

mmv1/templates/terraform/pre_update/alloydb_cluster.go.erb

@@ -1,8 +1,3 @@
-// Restrict modification of cluster_type from PRIMARY to SECONDARY as it is an invalid operation
-if d.HasChange("cluster_type") && d.Get("cluster_type") == "SECONDARY" {
-    return fmt.Errorf("Can not convert a primary cluster to a secondary cluster.")
-}
-
 // Restrict setting secondary_config if cluster_type is PRIMARY
 if d.Get("cluster_type") == "PRIMARY" && !tpgresource.IsEmptyValue(reflect.ValueOf(d.Get("secondary_config"))) {
     return fmt.Errorf("Can not set secondary config for primary cluster.")