Error occurs when creating Kendra as `staging` parameter because of length limit

[icoxfog417]

Bug Description As a developer who deploy GenU by npm run cdk:deploy -- -c env=staging encounters error when creating Kendra.

Steps to Reproduce Steps to reproduce the behavior:

1. Modify staging section of parameter.ts
2. Deploy GenU by npm run cdk:deploy -- -c env=staging with ragEnabled : true
3. Encounter error

Expected Behavior Kendra is deployed successfully

Background of this error

Kendra's index name is defined ad name: generative-ai-use-cases-index${envSuffix}, in rag.ts. However, maximum length of Kendra Index seems to be 31 therefore generative-ai-use-cases-indexstaging exceedes limit of length.

[tbrand]

related https://github.com/aws-samples/generative-ai-use-cases/issues/855