Require omnibus 8 or later
Require omnibus 8 or later

I bumped us from 5->6, but the change that needed to be done was
actually 5 -> 8.

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

aerobase/omnibus-software,chef/omnibus-software,mattray/omnibus-software,chef/omnibus-software,chef/omnibus-software,aerobase/omnibus-software,aerobase/omnibus-software,chef/omnibus-software,chef/omnibus-software,mattray/omnibus-software,chef/omnibus-software,mattray/omnibus-software,mattray/omnibus-software,aerobase/omnibus-software,aerobase/omnibus-software,mattray/omnibus-software