remove &$var reference notations in phpdoc

this isn't required by the spec and PHPStan chokes on it. I was previously having it ignore these errors, but it turns out that PHPStan is not making use of extended typeinfo provided if it can't parse the tag, which is problematic on level 6 and also a problem for array-of-type. Therefore, we are going to have to take the hit.

src/pocketmine/MemoryManager.php

@@ -472,9 +472,9 @@ class MemoryManager{
 
 	/**
 	 * @param mixed    $from
-	 * @param mixed    &$data
-	 * @param object[] &$objects
-	 * @param int[]    &$refCounts
+	 * @param mixed    $data reference parameter
+	 * @param object[] $objects reference parameter
+	 * @param int[]    $refCounts reference parameter
 	 * @param int      $recursion
 	 * @param int      $maxNesting
 	 * @param int      $maxStringSize