This was removed between 6.8.0.dev2411020930 and 6.8.0 final, but
results in a build failure if missing (or at least with Qt6.8.1).

qwebengineframe.sip:52:64: error: invalid use of incomplete type 'class QVariant'
--- a/sip/QtWebEngineCore/qwebengineframe.sip
+++ b/sip/QtWebEngineCore/qwebengineframe.sip
@@ -29,4 +29,8 @@
 %End
 
+%TypeCode
+#include <QVariant>
+%End
+
 public:
     bool isValid() const;