Remove duplicate $logger definition (#1272)

- The LoggerAwareTrait already defines it.

module/VuFind/src/VuFind/ILS/Driver/KohaILSDI.php

@@ -32,7 +32,6 @@ use PDO;
 use PDOException;
 use VuFind\Date\DateException;
 use VuFind\Exception\ILS as ILSException;
-use Zend\Log\LoggerInterface;
 
 /**
  * VuFind Driver for Koha, using web APIs (ILSDI)
@@ -106,13 +105,6 @@ class KohaILSDI extends \VuFind\ILS\Driver\AbstractBase implements
      */
     protected $db;
 
-    /**
-     * Logger Status
-     *
-     * @var LoggerInterface
-     */
-    protected $logger = false;
-
     /**
      * Date converter object
      *