[ROCm] reduce batch size to fix CI error (#15714)
ROCm CI batch size test occasionally fail. Try reduce batch size to fix
it.
error log:
Non-zero status code returned while running FusedMatMul node.
Name:'MatMul_2914_Grad/FusedMatMul_0' Status Message: HIP error
hipErrorNotFound:named symbol not found
Non-zero status code returned while running Gemm node.
Name:'MatMul_2891_Grad/Gemm_5' Status Message: HIP error
hipErrorNotFound:named symbol not found
