Examples: Use signals, slots instead of Q_SIGNALS, Q_SLOTS

Change-Id: I79a352d1bac11edf2d2b0443d2f1bb202fb4e254
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 65d9593413455e401e44006b07c555f27c293add)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

examples/dbus/remotecontrolledcar/car/car.h

@@ -14,13 +14,13 @@ public:
     Car();
     QRectF boundingRect() const;
 
-public Q_SLOTS:
+public slots:
     void accelerate();
     void decelerate();
     void turnLeft();
     void turnRight();
 
-Q_SIGNALS:
+signals:
     void crashed();
 
 protected:

examples/widgets/itemviews/spreadsheet/printview.h

@@ -16,7 +16,7 @@ class PrintView : public QTableView
 public:
     PrintView();
 
-public Q_SLOTS:
+public slots:
     void print(QPrinter *printer);
 };