Remove the reference to the CoreOS guide.

It appears the guide was removed from the website some time
  before as well. I guess the old content lives here now:
  https://github.com/weaveworks-guides/old-guides/tree/master/coreos-simple

site/install/installing-weave.md

@@ -48,8 +48,6 @@ To disable this check, run the following before launching Weave Net:
 
 ### Guides for Specific Platforms
 
-CoreOS users see [here](/guides/networking-docker-containers-with-weave-on-coreos/) for an example of installing Weave using cloud-config.
-
 Amazon ECS users see [here](https://www.weave.works/docs/scope/latest/ami/)
 for the latest Weave AMIs.