Switch to isUsingItem()

I don't plan on using this, as you informed me on discord that I didn't need the extra step, and it's a BC break anyway

src/pocketmine/Player.php

@@ -2542,7 +2542,7 @@ class Player extends Human implements CommandSender, ChunkLoader, IPlayer{
 							}
 						}
 
-						if($this->startAction === -1){
+						if(!$this->isUsingItem()){
 							$this->setUsingItem(true);
 							return true;
 						}