remove slug from EnvironmentsTest

Author: Daniel André Eikeland

test/Gitlab/Tests/Api/EnvironmentsTest.php

@@ -46,7 +46,6 @@ public function shouldCreateEnvironment()
 
         $params = array(
             'name' => 'review/fix-baz',
-            'slug' => 'review-fix-baz-dfjre5',
             'external_url' => 'https://review-fix-baz-dfjre5.example.gitlab.com'
         );