[ticket/14161] Wrong var name for core.download_file_send_to_browser_…

…before

`extension` must be `extensions`

Introduced in fix of PHPBB3-14101 (PR phpbbGH-3831)

PHPBB3-14161

phpBB/download/file.php

@@ -258,7 +258,7 @@
 	* @var	array	attachment			Array with attachment data
 	* @var	int		display_cat			Attachment category
 	* @var	int		download_mode		File extension specific download mode
-	* @var	array	extension			Array with file extensions data
+	* @var	array	extensions			Array with file extensions data
 	* @var	string	mode				Download mode
 	* @var	bool	thumbnail			Flag indicating if the file is a thumbnail
 	* @since 3.1.6-RC1
@@ -268,7 +268,7 @@
 		'attachment',
 		'display_cat',
 		'download_mode',
-		'extension',
+		'extensions',
 		'mode',
 		'thumbnail',
 	);