Fix tests for 5.3

tests/Monolog/Formatter/GelfMessageFormatterTest.php

@@ -129,11 +129,11 @@ class GelfMessageFormatterTest extends \PHPUnit_Framework_TestCase
             'level' => Logger::ERROR,
             'level_name' => 'ERROR',
             'channel' => 'meh',
-            'context' => array('from' => 'logger', 'exception' => [
+            'context' => array('from' => 'logger', 'exception' => array(
                 'class' => '\Exception',
                 'file'  => '/some/file/in/dir.php:56',
-                'trace' => ['/some/file/1.php:23', '/some/file/2.php:3']
-            ]),
+                'trace' => array('/some/file/1.php:23', '/some/file/2.php:3')
+            )),
             'datetime' => new \DateTime("@0"),
             'extra' => array(),
             'message' => 'log'