test: Simplify BF16 triton dtype selection in identity_test

[yinggeh]

What does the PR do?

Removes the identity_bf16 special-case when choosing the Triton input datatype in identity_test.py. Since np_to_triton_dtype(ml_dtypes.bfloat16) == "BF16", a single triton_type = np_to_triton_dtype(input_data.dtype) covers every model, including BF16.

Checklist

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• Added test plan and verified test passes.
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Commit Type:

• test

Where should the reviewer start?

qa/L0_backend_identity/identity_test.py

Test plan:

Exercised by L0_backend_identity.

• CI Pipeline ID: 55062265

Caveats:

Cosmetic cleanup; no behavior change (the explicit "BF16" string and np_to_triton_dtype(ml_dtypes.bfloat16) resolve to the same datatype).