local_dot_product_cuda fails when queries and keys have different lengths

[tridao]

There's an error when local_dot_product_cuda is called with different query and key lengths, because of a wrong reshape on this line:

fast-transformers/fast_transformers/local_product/local_product_cuda.cu

Line 512 in f22c137

keys.reshape({N*H, L, E}),

I think instead of

keys.reshape({N*H, L, E})

it should be

keys.reshape({N*H, S, E})