[ticket/15663] Move constant to compatibility_globals

PHPBB3-15663

phpBB/includes/constants.php

@@ -167,7 +167,6 @@ define('CONFIRM_REPORT', 4);
 define('ATTACHMENT_CATEGORY_NONE', 0);
 define('ATTACHMENT_CATEGORY_IMAGE', 1); // Inline Images
 define('ATTACHMENT_CATEGORY_THUMB', 4); // Not used within the database, only while displaying posts
-define('ATTACHMENT_CATEGORY_FLASH', 5); // Flash/SWF files
 
 // BBCode UID length
 define('BBCODE_UID_LEN', 8);