update README

README.md

@@ -351,7 +351,7 @@ No modules.
 | <a name="input_is_primary_cluster"></a> [is\_primary\_cluster](#input\_is\_primary\_cluster) | Determines whether cluster is primary cluster with writer instance (set to `false` for global cluster and replica clusters) | `bool` | `true` | no |
 | <a name="input_kms_key_id"></a> [kms\_key\_id](#input\_kms\_key\_id) | The ARN for the KMS encryption key. When specifying `kms_key_id`, `storage_encrypted` needs to be set to `true` | `string` | `null` | no |
 | <a name="input_manage_master_user_password"></a> [manage\_master\_user\_password](#input\_manage\_master\_user\_password) | Set to true to allow RDS to manage the master user password in Secrets Manager. Cannot be set if `master_password` is provided | `bool` | `true` | no |
-| <a name="input_manage_master_user_password_rotation"></a> [manage\_master\_user\_password\_rotation](#input\_manage\_master\_user\_password\_rotation) | Whether to manage the master user password rotation. Setting this value to false after previously having been set to true will disable automatic rotation. | `bool` | `false` | no |
+| <a name="input_manage_master_user_password_rotation"></a> [manage\_master\_user\_password\_rotation](#input\_manage\_master\_user\_password\_rotation) | Whether to manage the master user password rotation. By default, false on creation, rotation is managed by RDS. There is not currently a way to disable this on initial creation even when set to false. Setting this value to false after previously having been set to true will disable automatic rotation. | `bool` | `false` | no |
 | <a name="input_master_password"></a> [master\_password](#input\_master\_password) | Password for the master DB user. Note that this may show up in logs, and it will be stored in the state file. Required unless `manage_master_user_password` is set to `true` or unless `snapshot_identifier` or `replication_source_identifier` is provided or unless a `global_cluster_identifier` is provided when the cluster is the secondary cluster of a global database | `string` | `null` | no |
 | <a name="input_master_user_password_rotate_immediately"></a> [master\_user\_password\_rotate\_immediately](#input\_master\_user\_password\_rotate\_immediately) | Specifies whether to rotate the secret immediately or wait until the next scheduled rotation window. | `bool` | `null` | no |
 | <a name="input_master_user_password_rotation_automatically_after_days"></a> [master\_user\_password\_rotation\_automatically\_after\_days](#input\_master\_user\_password\_rotation\_automatically\_after\_days) | Specifies the number of days between automatic scheduled rotations of the secret. Either `master_user_password_rotation_automatically_after_days` or `master_user_password_rotation_schedule_expression` must be specified | `number` | `null` | no |