[Tests] Update audio classification tests to support torch 1.10
# What does this PR do?

The recent changes to `torch.nn.GroupNorm()` algorithm made it work slightly differently for inputs with small standard deviations. This is most noticeable (`~1e-3`) for uniform inputs like `np.ones()` in `test_small_model_pt()` and less noticeable (`<1e-5`) for other audio classification tests. 
The ASR models are not affected, since they don't use mean-pooling over outputs and thus don't amplify the difference as much.

PyTorch response: https://github.com/pytorch/pytorch/issues/67907
