Projectile: fixed move() not using the given parameters (#4481)

it was using this->motion instead, which usually would be the same, but maybe not.

src/pocketmine/entity/projectile/Projectile.php

@@ -180,7 +180,7 @@ abstract class Projectile extends Entity{
 		Timings::$entityMoveTimer->startTiming();
 
 		$start = $this->asVector3();
-		$end = $start->add($this->motion);
+		$end = $start->add($dx, $dy, $dz);
 
 		$blockHit = null;
 		$entityHit = null;