fix: cross account private hub model fine-tuning

[malav-shastri]

Issue #, if available:

Description of changes:

• Fixing Cross Account private hub model fine-tuning

Testing done:

• Current Unit tests/ integ tests
• Notebook tests: PrivateHub Model Deployment and Training, PrivateHub Cross account model deployment and training

Merge Checklist

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General

• I have read the CONTRIBUTING doc
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Tests

• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added unit and/or integration tests as appropriate to ensure backward compatibility of the changes
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• I have used unique_name_from_base to create resource names in integ tests (if appropriate)

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[AWS-pratab]

Looks good.

Are there any corresponding unit tests to update for the cache util?