Clarify the OS feature support gap versus installation method

We presently say that we don't provide a binary installation method on Linux, Windows, and Mac in features.yml. But we actually do provide a fantastic binary installation on Linux in our Omnibus packages, however we do not support Mac and windows: https://docs.gitlab.com/ee/install/requirements.html

We should update the missing feature to be Windows and OSX support, rather than a binary installation method.