[NVIDIA XLA] Skip TestCudnnConvInt8x32Bias test for sm 6.0 and earlier
cudnnConvolutionBiasActivationForward() for int8 is only supported on GPUs with compute capability 6.1 or later.
This PR disables TestCudnnConvInt8x32Bias which currently fails on SM 6.0 GPUs, such as P100.