r/aws_rds_cluster: tweak storage_type argument docs

website/docs/r/rds_cluster.html.markdown

@@ -263,7 +263,7 @@ The following arguments are supported:
 * `snapshot_identifier` - (Optional) Specifies whether or not to create this cluster from a snapshot. You can use either the name or ARN when specifying a DB cluster snapshot, or the ARN when specifying a DB snapshot. Conflicts with `global_cluster_identifier`. Clusters cannot be restored from snapshot **and** joined to an existing global cluster in a single operation. See the [AWS documentation](https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/aurora-global-database-getting-started.html#aurora-global-database.use-snapshot) or the [Global Cluster Restored From Snapshot example](#global-cluster-restored-from-snapshot) for instructions on building a global cluster starting with a snapshot.
 * `source_region` - (Optional) The source region for an encrypted replica DB cluster.
 * `storage_encrypted` - (Optional) Specifies whether the DB cluster is encrypted. The default is `false` for `provisioned` `engine_mode` and `true` for `serverless` `engine_mode`. When restoring an unencrypted `snapshot_identifier`, the `kms_key_id` argument must be provided to encrypt the restored cluster. Terraform will only perform drift detection if a configuration value is provided.
-* `storage_type` - (Optional) (Required for Multi-AZ DB cluster) (Forces new for Multi-AZ DB cluster) Specifies the storage type to be associated with the DB cluster. For Aurora DB cluster, non-destructive mutation of `storage_type`. Valid values for Aurora DB cluster: `<blank string>`, `aurora-iopt1`, Default: `<blank string>`. Valid values for Multi-AZ DB cluster: `io1`, Default: `io1`.
+* `storage_type` - (Optional) (Required for Multi-AZ DB clusters) (Forces new for Multi-AZ DB clusters) Specifies the storage type to be associated with the DB cluster. For Aurora DB clusters, `storage_type` modifications can be done in-place. For Multi-AZ DB Clusters, the `iops` argument must also be set. Valid values are: `""`, `aurora-iopt1` (Aurora DB Clusters); `io1` (Multi-AZ DB Clusters). Default: `""` (Aurora DB Clusters); `io1` (Multi-AZ DB Clusters).
 * `tags` - (Optional) A map of tags to assign to the DB cluster. If configured with a provider [`default_tags` configuration block](https://registry.terraform.io/providers/hashicorp/aws/latest/docs#default_tags-configuration-block) present, tags with matching keys will overwrite those defined at the provider-level.
 * `vpc_security_group_ids` - (Optional) List of VPC security groups to associate with the Cluster