chore(fsx): backfill missing enums for fsx (#33649)

### Description of changes
backfill missing enums for fsx

### Checklist
- [x] 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)

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

Author: paulhcsun

packages/aws-cdk-lib/aws-fsx/lib/file-system.ts

@@ -14,6 +14,10 @@ export enum StorageType {
    * Hard Disk Drive storage
    */
   HDD = 'HDD',
+  /**
+   * Intelligent Tiering storage
+   */
+  INTELLIGENT_TIERING = 'INTELLIGENT_TIERING',
 }
 
 /**