refactor(cli): remove unused code (#33096)

### Reason for this change

This file is completely unused in our code base.
The test also doesn't test anything by indirection.

### Description of changes

Removed the unused file and test.

### Describe any new or updated permissions being added

n/a

### Description of how you validated changes

Searched for the function on GitHub and internally. All found references
are copies of the CDK code base and don't represent actual usage of the
exported function.

### 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: mrgrain