Update documentation for IPv6 with DocumentDB

Author: A1bi

website/docs/r/docdb_cluster.html.markdown

@@ -71,6 +71,7 @@ This resource supports the following arguments:
   show up in logs. Please refer to the DocumentDB Naming Constraints. Conflicts with `master_password` and `manage_master_user_password`.
 * `master_password_wo_version` - (Optional) Used together with `master_password_wo` to trigger an update. Increment this value when an update to the `master_password_wo` is required.
 * `master_username` - (Required unless a `snapshot_identifier` or unless a `global_cluster_identifier` is provided when the cluster is the "secondary" cluster of a global database) Username for the master DB user.
+* `network_type` - The network type of the DB cluster (`IPV4` or `DUAL`).
 * `port` - (Optional) The port on which the DB accepts connections
 * `preferred_backup_window` - (Optional) The daily time range during which automated backups are created if automated backups are enabled using the BackupRetentionPeriod parameter.Time in UTC
 Default: A 30-minute window selected at random from an 8-hour block of time per regionE.g., 04:00-09:00

website/docs/r/docdb_subnet_group.html.markdown

@@ -40,6 +40,7 @@ This resource exports the following attributes in addition to the arguments abov
 
 * `id` - The docDB subnet group name.
 * `arn` - The ARN of the docDB subnet group.
+* `supported_network_types` - The network type of the docDB subnet group (`IPV4` or `DUAL`).
 * `tags_all` - A map of tags assigned to the resource, including those inherited from the provider [`default_tags` configuration block](https://registry.terraform.io/providers/hashicorp/aws/latest/docs#default_tags-configuration-block).
 
 ## Import