Sketcher: Enable undo when trimming
Sketcher: Enable undo when trimming

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Reported here:
https://forum.freecadweb.org/viewtopic.php?p=311853#p312647

Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master