QtSupport: Set a lower single step in ExamplesPageWidget view

By default, the view scrolls by a whole row when using arrow keys or
mouse wheel. With rows with a height as in the examples view, this
causes more of a fast flickering than the impression of a scrolling.

The single step value of 25 which is set by this change makes it look
smoother.

Change-Id: I7fe9fe49dab71cebdfd8b01eef245813783426ae
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/qtsupport/gettingstartedwelcomepage.cpp

@@ -51,6 +51,7 @@
 #include <QMessageBox>
 #include <QPainter>
 #include <QPushButton>
+#include <QScrollBar>
 #include <QStyledItemDelegate>
 #include <QTimer>
 
@@ -316,6 +317,8 @@ public:
         auto gridView = new GridView(this);
         gridView->setModel(&m_gridModel);
         gridView->setItemDelegate(&m_exampleDelegate);
+        if (auto sb = gridView->verticalScrollBar())
+            sb->setSingleStep(25);
         vbox->addWidget(gridView);
 
         connect(&m_exampleDelegate, &ExampleDelegate::tagClicked,