README: update routing.git URL

The routing packages feed moved from `openwrt-routing/packages` to
`openwrt/routing`, reflect that in the README.

Signed-off-by: Paul Spooren <mail@aparcar.org>

README.md

@@ -57,8 +57,8 @@ packages to OpenWrt, please find the fitting repository below.
 * [OpenWrt Packages](https://github.com/openwrt/packages): Community repository
   of ported packages.
 
-* [OpenWrt Routing](https://github.com/openwrt-routing/packages): Packages
-  specifically focused on (mesh) routing.
+* [OpenWrt Routing](https://github.com/openwrt/routing): Packages specifically
+  focused on (mesh) routing.
 
 ## Support Information