Updated deprecation status for "repository:shortid"
Updated deprecation status for "repository:shortid"

The `repository:shortid` syntax for referencing images is very little used,
collides with with tag references can be confused with digest references.

The `repository:shortid` notation was deprecated in Docker 1.13, and scheduled
for removal in Docker 17.12.

This patch updates the deprecation status for this feature.

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

ashfall/cli,cpuguy83/cli,dnephin/cli,cpuguy83/cli,docker/cli,dnephin/cli,thaJeztah/cli,ashfall/cli,thaJeztah/cli,docker/cli