test: fix sagemaker input size test

[mattwittwer]

What does the PR do?

This PR fixes an test error introduced in #8686. The sagemaker input size test fails in the pipeline. This is resolved by switching from the SageMaker sm_model to the identity_fp32 model. Matching the test used in: #8685

Checklist

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• Related issues are referenced.
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• Added test plan and verified test passes.
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Commit Type:

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• build
• ci
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• fix
• perf
• refactor
• revert
• style
• test

Related PRs:

#8686

Where should the reviewer start?

Test plan:

• CI Pipeline ID:

45931145

Caveats:

Background

Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

• closes GitHub issue: #xxx

[whoisj]

approved assuming CI passes.