Arch docs: Updated dependencies to match AUR

The AUR packages lxc-docker and lxc-docker-git have changed their dependencies.

docs/sources/installation/archlinux.rst

@@ -26,8 +26,8 @@ Dependencies
 Docker depends on several packages which are specified as dependencies in
 either AUR package.
 
-* aufs3
 * bridge-utils
+* device-mapper
 * go
 * iproute2
 * lxc