feat(eks): backfill missing enums for eks (#33646)

### Description of changes
backfill missing enums for eks
### 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-eks/lib/managed-nodegroup.ts

@@ -103,6 +103,10 @@ export enum CapacityType {
    * on-demand instances
    */
   ON_DEMAND = 'ON_DEMAND',
+  /**
+   * capacity block instances
+   */
+  CAPACITY_BLOCK = 'CAPACITY_BLOCK',
 }
 
 /**