removed invalid wikidata key in XMPP front matter

topics/xmpp/index.md

@@ -8,6 +8,5 @@ short_description: XMPP is the open standard for messaging and presence.
 topic: xmpp
 url: https://xmpp.org/
 wikipedia_url: https://en.wikipedia.org/wiki/XMPP
-wikidata: Q188951
 ---
 XMPP is the Extensible Messaging and Presence Protocol, a set of open technologies for instant messaging, presence, multi-party chat, voice and video calls, collaboration, lightweight middleware, content syndication, and generalized routing of XML data.