docs(rds): correct default StorageType in DatabaseCluster (#34530)

### Issue # (if applicable)

Closes #34376.

### Reason for this change



### Description of changes

This PR corrects the JSDoc comment for the `storageType` property in `DatabaseCluster`. According to CloudFormation documentation, the default value for Aurora clusters is `aurora` (Aurora Standard), not `aurora-iopt1` (Aurora I/O Optimized) as incorrectly documented.
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-rds-dbcluster.html#cfn-rds-dbcluster-storagetype



### Describe any new or updated permissions being added




### Description of how you validated changes



### Checklist
- [ ] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: ykethan

packages/aws-cdk-lib/aws-rds/lib/cluster.ts

@@ -365,7 +365,7 @@ interface DatabaseClusterBaseProps {
   /**
    * The storage type to be associated with the DB cluster.
    *
-   * @default - DBClusterStorageType.AURORA_IOPT1
+   * @default - DBClusterStorageType.AURORA
    */
   readonly storageType?: DBClusterStorageType;