use https for help

src/app/qgsoptions.cpp

@@ -299,7 +299,7 @@ QgsOptions::QgsOptions( QWidget *parent, Qt::WindowFlags fl, const QList<QgsOpti
   connect( mBtnRemoveHiddenPath, &QAbstractButton::clicked, this, &QgsOptions::removeHiddenPath );
 
   //locations of the QGIS help
-  const QStringList helpPathList = mSettings->value( QStringLiteral( "help/helpSearchPath" ), "http://docs.qgis.org/$qgis_short_version/$qgis_locale/docs/user_manual/" ).toStringList();
+  const QStringList helpPathList = mSettings->value( QStringLiteral( "help/helpSearchPath" ), "https://docs.qgis.org/$qgis_short_version/$qgis_locale/docs/user_manual/" ).toStringList();
   for ( const QString &path : helpPathList )
   {
     QTreeWidgetItem *item = new QTreeWidgetItem();