doc/pacman.conf: ParallelDownloads expects a value

This can not be specified on its own but requires a value.
Signed-off-by: Christian Hesse <mail@eworm.de>
Signed-off-by: Allan McRae <allan@archlinux.org>

doc/pacman.conf.5.asciidoc

@@ -202,7 +202,7 @@ Options
 	Disable defaults for low speed limit and timeout on downloads. Use this
 	if you have issues downloading files with proxy and/or security gateway.
 
-*ParallelDownloads*::
+*ParallelDownloads =* ...::
 	Specifies number of concurrent download streams. The value needs to be a
 	positive integer. If this config option is not set then only one download
 	stream is used (i.e. downloads happen sequentially).