Make left-click toggle package selection

src/modules/packagechooser/PackageChooserPage.cpp

@@ -40,7 +40,7 @@ PackageChooserPage::PackageChooserPage( PackageChooserMode mode, QWidget* parent
     case PackageChooserMode::OptionalMultiple:
         [[fallthrough]];
     case PackageChooserMode::RequiredMultiple:
-        ui->products->setSelectionMode( QAbstractItemView::ExtendedSelection );
+        ui->products->setSelectionMode( QAbstractItemView::MultiSelection );
     }
 
     ui->products->setMinimumWidth( 10 * CalamaresUtils::defaultFontHeight() );