Drop duplicate 'using namespace' directive

Change-Id: If235c37cf52cfbfd171a6d1784cf5940c162332a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/112618
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
diff --git a/cui/source/dialogs/QrCodeGenDialog.cxx b/cui/source/dialogs/QrCodeGenDialog.cxx
index 28bbfab..3de87ab 100644
--- a/cui/source/dialogs/QrCodeGenDialog.cxx
+++ b/cui/source/dialogs/QrCodeGenDialog.cxx
@@ -52,7 +52,6 @@ using namespace css::container;
using namespace css::frame;
using namespace css::io;
using namespace css::lang;
using namespace css::frame;
using namespace css::sheet;
using namespace css::text;
using namespace css::drawing;