Keep Wikidata on our mw1.23-wmf19 branch for now

We reverted deployment of mw1.23-wmf21 due to
date formatting / localisation issues.

We will stay on mw1.23-wmf19 and wait until
we make a new branch in a couple weeks.

Change-Id: Id560f799911e566a936e776354f0cc2b10bd0813