Origin "m4" docs redirect to "latest" docs

[tiwillia]

The Origin m4 docs appear to be inaccessible. The drop down on https://docs.openshift.org/index.html has two links, "Origin m4" -> "origin-m4/index.html" and "Origin Latest" -> "latest/index.html". Both of these links lead to https://docs.openshift.org/latest/welcome/index.html

[adellape]

cc @nhr per recent discussion on updating the drop-down for Origin docs.

[tiwillia]

Due to this, pages like the cartridge developers guide http://docs.openshift.org/origin-m4/oo_cartridge_developers_guide.html are completely inacessible.

[adellape]

We ended up removing the M4 docs from the site entirely via #2819. The source is still available via https://github.com/openshift/origin-server/tree/master/documentation.