CraftingTransaction: remove impossible condition

this is never hit thanks to the logic flow above - recipeItems is never empty.

src/pocketmine/inventory/transaction/CraftingTransaction.php

@@ -108,9 +108,6 @@ class CraftingTransaction extends InventoryTransaction{
 			}
 		}
 
-		if($iterations < 1){
-			throw new TransactionValidationException("Tried to craft zero times");
-		}
 		if(count($txItems) > 0){
 			//all items should be destroyed in this process
 			throw new TransactionValidationException("Expected 0 ingredients left over, have " . count($txItems));