fix isGrounded check (#774)

src/field/pokemon.ts

@@ -940,7 +940,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   }
 
   isGrounded(): boolean {
-    return !this.isOfType(Type.FLYING, true) && this.getAbility().id !== Abilities.LEVITATE && !!this.getTag(BattlerTagType.GROUNDED);
+    return !this.isOfType(Type.FLYING, true) && this.hasAbility(Abilities.LEVITATE);
   }
 
   getAttackMoveEffectiveness(source: Pokemon, move: PokemonMove): TypeDamageMultiplier {