Sketcher: Avoid single tangency plus coincident when preexisting single tangency
Sketcher: Avoid single tangency plus coincident when preexisting single tangency

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fixes #3299 (remaining)

Draw a line. Draw an arc. Make edge to edge tangency. Select endpoints. Try to create a coincident constraint. You now get an Endpoint-to-Endpoint tangency.

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