In the context of working on T280627: Investigation of remaining page_props update issue [timebox: 2 days] it was noticed that the ChangeHandler class doesn't use the injected SiteLookup service anymore. This task is about cleaning up that dead code.
History of this bit of code as far as I can tell:
- introduced in October 7th 2015 with one usage: https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/243402
- that one usage was removed October 29th 2015: https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/238137 in context of T111521
- the now unused injection was from SiteStore ot SiteLookup in December 21st 2016: https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/328413