Add Hau as a potential Champion

This fixes the Generation 7 Elite Four not having a corresponding Champion to go along with them.

src/data/biomes.ts

@@ -7614,6 +7614,7 @@ export const biomeTrainerPools: BiomeTrainerPools = {
     [ TrainerType.ALDER, [] ],
     [ TrainerType.IRIS, [] ],
     [ TrainerType.DIANTHA, [] ],
+    [ TrainerType.HAU, [] ],
     [ TrainerType.LEON, [] ],
     [ TrainerType.GEETA, [] ],
     [ TrainerType.NEMONA, [] ],