Add ruby 2.5.4 and 2.6.2
Add ruby 2.5.4 and 2.6.2

This includes a updated rubygems with several CVEs fixed and also fixed
some bugs.

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

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