Change “the Wikidata software“ to “the software behind Wikidata”

Requested by Lydia – there’s no space in the thesis to fully introduce
the distinction between Wikibase and Wikidata, but we can at least be a
bit more correct in this phrasing.

sections/background.tex

@@ -278,7 +278,7 @@ \section{Wikidata}
 The community has several ways to describe \glspl{schema} to varying degrees of formality
 (such as \gls{property} lists on WikiProject pages or the property constraints system),
 but they are all realized by community consensus,
-not enforced by the \gls{Wikidata} software.
+not enforced by the software behind \gls{Wikidata}.
 The great flexibility which this lends to the community
 is considered to be one of \gls{Wikidata}’s greatest strengths \cite{vrandecic-restricting-the-world},
 and though the use of \acrlong{shex}