Fix dimensions of 97_ScaledDotProductAttention

[arielge]

In the context of torch.nn.functional.scaled_dot_product_attention, the input tensors have shape (batch_size, num_heads, sequence_length, head_dim), where head_dim is the dimension per attention head.

The total model embedding dimension equals num_heads × head_dim, so for a model with embedding dimension of 1024 and 32 heads, the appropriate dimension would be 32.