[Chore] Update CODEOWNERS for new CI infrastructure
[Chore] Update CODEOWNERS for new CI infrastructure

`.buildkite` is gone, replaced with `.expeditor`

Also went ahead and removed the line for `components/backline`, since
a) there were no names anyway, and b) there's not really any code to
that component.

Signed-off-by: Christopher Maier <b4598f17a90ef80817bae8ad6c37249740caafb4@chef.io>

habitat-sh/habitat,rsertelon/habitat,rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,rsertelon/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat,habitat-sh/habitat