package/libass: update the upstream URL in Config.in

Update the upstream URL in the help text in Config.in. This
addresses the 'Invalid(405)' URL status in the package stats
web page output.

Signed-off-by: Mark Corbin <mark@dibsco.co.uk>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libass/Config.in

@@ -6,4 +6,4 @@ config BR2_PACKAGE_LIBASS
 	  libass is a portable subtitle renderer for the ASS/SSA
 	  (Advanced Substation Alpha/Substation Alpha) subtitle format
 
-	  http://code.google.com/p/libass/
+	  https://github.com/libass/libass