Fix eject model tests for Triton

[wanliAlex]

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  Fix eject model tests for Triton

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Note

Low Risk
Test-only changes that update assertions for eject_model behavior and messages; low risk aside from potentially masking real API regressions if the new success-on-miss behavior is unintended.

Overview
Updates test_model_cache_management to align with Triton/model-cache behavior: switches the default OpenCLIP model used in tests, treats ejection of a non-cached model as a successful no-op (instead of raising MarqoWebError), and loosens/normalizes success message assertions to match the current response text.

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