Revert "Item: restrict bounds of count to 0-255"

This reverts commit 10317527e4.

this breaks user code which exceeds stack limits in legitimate
circumstances. For example, it should be OK to add 6000x diamond to a
player's inventory without being forced to manually split the count up
for addItem().

src/pocketmine/item/Item.php

@@ -557,10 +557,6 @@ class Item implements ItemIds, \JsonSerializable{
 	 * @return $this
 	 */
 	public function setCount(int $count) : Item{
-		if($count < 0 or $count > 255){
-			throw new \InvalidArgumentException("Count must be in the range 0-255");
-		}
-
 		$this->count = $count;
 
 		return $this;