Help: Use Qt5-style connects

The heavy lifting was done by clazy.

Change-Id: Ied9c7fcc031e530c41b342de950e2f0ac730bbb1
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/help/helpwidget.h

@@ -78,7 +78,7 @@ public:
                           bool newPage = false);
     void activateSideBarItem(const QString &id);
 
-public slots:
+public:
     void setSource(const QUrl &url);
     void updateCloseButton();
 
@@ -92,13 +92,12 @@ signals:
     void sourceChanged(const QUrl &url);
     void filterActivated(const QString &name);
 
-private slots:
+private:
     void updateBackMenu();
     void updateForwardMenu();
     void updateWindowTitle();
     void helpModeButtonClicked();
 
-private:
     void goHome();
     void addBookmark();
     void copy();