Add some new battle backgrounds

src/arena.ts

@@ -99,8 +99,6 @@ export class Arena {
 
   getBiomeKey(): string {
     switch (this.biomeType) {
-      case Biome.TOWN:
-        return 'plains';
       case Biome.TALL_GRASS:
         return 'grass';
       case Biome.CITY:

src/data/biome.ts

@@ -36,8 +36,6 @@ export enum Biome {
 
 export function getBiomeName(biome: Biome) {
   switch (biome) {
-    case Biome.TOWN:
-      return 'TOWN';
     case Biome.GRASS:
       return 'GRASSY FIELD';
     case Biome.RUINS: