QSimplex: API cleanup [2/3]: disable copying

QSimplex is not designed to be copied, so disable explicitly.

Change-Id: Ia1ddcfe905380e594930717c7c55bb38a7dd4059
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>

src/widgets/graphicsview/qsimplex_p.h

@@ -149,6 +149,7 @@ struct QSimplexConstraint
 
 class QSimplex
 {
+    Q_DISABLE_COPY(QSimplex)
 public:
     QSimplex();
     virtual ~QSimplex();