[ticket/14264] Don't use constants as return values

This will prevent BC breaking in the future if we decide to
get rid of constants.

PHPBB3-14264

phpBB/phpbb/textreparser/plugins/group_description.php

@@ -27,12 +27,4 @@ class group_description extends \phpbb\textreparser\row_based_plugin
 			'options'    => 'group_desc_options',
 		);
 	}
-
-	/**
-	* {@inheritdoc}
-	*/
-	public function get_table_name()
-	{
-		return GROUPS_TABLE;
-	}
 }