SDKv3-04: Update @aws-cdk/cloudformation-diff

[TheRealAmazonKendra]

Context

The AWS SDK V2 is being deprecated. We need to remove all uses of it from the CDK.

Task Description

The CloudFormation namespace is used in diff-template.ts. Remove this and update aws-cdk to also have the correct namespace when this is used.

Open Questions

1. aws-cdk must also be upgraded to make this change. Will it cause conflicts/issues to upgrade parts of aws-cdk at a time? If so, this will have to be done with several other tasks in one fell swoop. (I don't think this is the case, but it's worth mentioning)

Acceptance Criteria

1. Remove use of the v2 namespace in all locations.
2. All tests (unit and integ) still are passing after these changes.

[TheRealAmazonKendra]

#29730

[github-actions]

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