[PATCH] models: Remove 'latest_series'

[Stephen Finucane]

On Mon, 2018-09-10 at 14:45 -0600, Stephen Finucane wrote:
> This is only used in a single view (where it probably shouldn't be used)
> and some tests. It's an anti-pattern that makes it too easy to shoot
> yourself in the foot. Remove it.
> 
> Signed-off-by: Stephen Finucane <stephen at that.guru>

This was blocking my rebase of the series-patch relationship series so
I've gone ahead and applied it. If anyone sees any issues, we can fix
them with a follow-up.

Stephen