Change “Wikidata Query” to “Wikidata Query Service”
Wikidata Query  (WDQ) used to be an experimental querying service by
Magnus Manske; the service to which this repository provides the
frontend has always been called the Wikidata Query Service, in short
WDQS. Fix a few references to the incorrect name.
This becomes especially important because with change Ifafdffe49b
(commit e333fc57b8), the brand title is now used for the document title,
which should definitely contain the word “service”.