[ROCM] adjust test_flash_attn_rocm test tolerance (#21379)
The test_flash_attn_rocm.py from
https://github.com/microsoft/onnxruntime/pull/21032 failed frequently.
For example, I saw two failed jobs today:
E Max absolute difference: 0.002167
E Max absolute difference: 0.002686
Adjust the abs threshold from 0.002 to 0.005, and use default relative tolerance rtol=0.001.
