Offset2D of circle changes Z-plane

I am trying to make two concentric circles on the top face of a box for further extrusion. However this code produces two circles with the right offset, but in different Z planes.

```
r = cq.Workplane("XY")
r = r.box(1,1,1)
r = r.faces(">Z")
r = r.circle(0.75)
r = r.tag("c")

r = r.offset2D(0.1)
show_object(r)

r = r.wires(tag="c")
show_object(r)
```

I found a similar issue in FreeCAD ([https://tracker.freecadweb.org/view.php?id=3020](https://tracker.freecadweb.org/view.php?id=3020)) and it seems they had to manipulate the location before executing the offset2d operation: https://github.com/FreeCAD/FreeCAD/commit/dbc09e3a2342af8784045d3d0ae3565ec869bef6