Fix cattle-outbreak strain selection

In the process of fixing #131 (via #132) the genome tree was completely wrong due to filtering out all the strains we actually want! (Screenshot below). The strains were dropped by the clock filter in `augur refine`. Now that GenoFLU metadata is (or soon will be) available via #126 we should try restricting to `B3.13`. <img width="586" alt="Image" src="https://github.com/user-attachments/assets/2728b000-515f-49cd-90e2-cec2949f4b74" />