Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  21e9936ae7a9aec97391f0ef5bd568823e0dc1cd

i18n: replace single-quotes by double-quotes

Spotted by Base
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Wikibase-validator-missing-field/en

Change-Id: I811f56f1285d8a2734fd41e3607bfb66fed4f009