cmake-gui: Remove unused viewType slot

The slot for `setViewType(t)` and `viewType()` are never connected.
Found by Clazy (`const-signal-or-slot`).

Source/QtDialog/QCMakeCacheView.h

@@ -91,10 +91,6 @@ public slots:
                       const QString& description, const QVariant& value,
                       bool advanced);
 
-  // set the view type
-  void setViewType(ViewType t);
-  ViewType viewType() const;
-
 public:
   // get the properties
   QCMakePropertyList properties() const;
@@ -112,6 +108,10 @@ public:
   // get the data in the model for this property
   void getPropertyData(const QModelIndex& idx1, QCMakeProperty& prop) const;
 
+  // set the view type
+  void setViewType(ViewType t);
+  ViewType viewType() const;
+
 protected:
   bool EditEnabled;
   int NewPropertyCount;