Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  1630fc2ab5ed3d3533f11e69fa3cf4965304b091

Drop unused EntityRevisionSerializer

Please note that I'm not 100% sure if simply deleting this is ok.
But if all tests succeed it should be, right?

Change-Id: Ib22ac4f54beb4dd288ac0d57acc96f46550969d5