Remove: ZOOM_LVL_COUNT

This is the only enumeration with a COUNT and END. The logic of the COUNT
implied that BEGIN could be non-zero, but all but two uses of zoom level
assume that BEGIN is zero, making the separate count only confusing.

src/spritecache.cpp

@@ -457,7 +457,7 @@ static void *ReadSprite(const SpriteCache *sc, SpriteID id, SpriteType sprite_ty
 
 	Debug(sprite, 9, "Load sprite {}", id);
 
-	SpriteLoader::Sprite sprite[ZOOM_LVL_COUNT];
+	SpriteLoader::Sprite sprite[ZOOM_LVL_END];
 	uint8_t sprite_avail = 0;
 	sprite[ZOOM_LVL_NORMAL].type = sprite_type;
 
@@ -1051,4 +1051,4 @@ void GfxClearFontSpriteCache()
 	}
 }
 
-/* static */ ReusableBuffer<SpriteLoader::CommonPixel> SpriteLoader::Sprite::buffer[ZOOM_LVL_COUNT];
+/* static */ ReusableBuffer<SpriteLoader::CommonPixel> SpriteLoader::Sprite::buffer[ZOOM_LVL_END];