layout->legend->tracegroupgap does not work, when orientation=h, since v1.46.0

[njclarke]

Since v1.46.0, when layout->legend->orientation=h, then layout->legend->tracegroupgap does not work. It works correctly in <=v1.45.3. Since v1.46.0 the value for tracegroupgap does not change the spacing when layout->legend->orientation=h.