Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  3c3d9b7fcc0e1ae4be8fe642f4e7fa5a133d9d92

Fix mistakes and general cleanup in Wikibase\Validators

Main changes are:
* Added missing private properties.
* Added missing array type hints.

This is split from I7434d5c.

Change-Id: I3a0fadea4bbc6c3c8fc530431b20d51d0a6c707b