QXdgDesktopPortalThemePlugin: includemocs

Including moc files directly into their classes' TU tends to improve
codegen and enables extended compiler warnings, e.g. about unused
private functions or fields.

Pick-to: 6.3 6.2 5.15
Task-number: QTBUG-102886
Change-Id: I564107743e093d880d7d201f45e44207055ad7cf
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/plugins/platformthemes/xdgdesktopportal/qxdgdesktopportalfiledialog.cpp

@@ -472,3 +472,5 @@ void QXdgDesktopPortalFileDialog::gotResponse(uint response, const QVariantMap &
 }
 
 QT_END_NAMESPACE
+
+#include "moc_qxdgdesktopportalfiledialog_p.cpp"