Fix: concat bcast

[sbrantq]

The pattern concat(broadcast(...), broadcast(...)) fires when the bcasts replicate values along the concat dimension.

In the MWE it gives something like

%cat = concat %arg0, %arg1, dim = 0 : (tensor<1xf32>, tensor<1xf32>) -> tensor<2xf32>
%out = broadcast_in_dim %cat, dims = [0] : (tensor<2xf32>) -> tensor<8xf32>