docs/website: fix manual symlink

It should point to the filesystem path on the server, not the HTTP virtual path.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/website/manual.html

@@ -1 +1 @@
-/downloads/manual/manual.html
+/var/www/downloads/buildroot/manual/manual.html