chore(ecr): backfill missing enums for ecr (aws#33643)

### Description of changes
backfill missing enums for ecr

### 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*

packages/aws-cdk-lib/aws-ecr/lib/repository.ts

@@ -1029,6 +1029,10 @@ export class RepositoryEncryption {
    * 'KMS'
    */
   public static readonly KMS = new RepositoryEncryption('KMS');
+  /**
+   * 'KMS_DSSE'
+   */
+  public static readonly KMS_DSSE = new RepositoryEncryption('KMS_DSSE');
 
   /**
    * @param value the string value of the encryption