Update Docblock to specify allowing string Log Levels (#1068)

src/Monolog/Handler/AbstractHandler.php

@@ -24,8 +24,8 @@ abstract class AbstractHandler extends Handler
     protected $bubble = true;
 
     /**
-     * @param int  $level  The minimum logging level at which this handler will be triggered
-     * @param bool $bubble Whether the messages that are handled can bubble up the stack or not
+     * @param int|string $level  The minimum logging level at which this handler will be triggered
+     * @param bool       $bubble Whether the messages that are handled can bubble up the stack or not
      */
     public function __construct($level = Logger::DEBUG, $bubble = true)
     {