use pessimistic version constraint

- this is compatible with gem versions from 10.28.0 with minimal
  changes.
- mixlib-shellout differs in windows-versus-unix due to version pinning
  in windows-pr picking up old mixlib-shellout on windows, this is
  not fix, and left similar to 10.28.0
- gem versions should be levelled up for 10.30.x and beyond
- newly built 10.28.0 will pick up new mixlib-config 2.0 which is
  a delta from the downloadable omnibus builds, 10.28.2 will not
  pick up mixlib-config 2.0