Don't always offset with 0.5mm

This is no longer needed, since before this happens we would already get an error with calculating the 3D model. Perhaps we should introduce a minkowski offset there but performing Minkowski on a 3D model is fairly expensive.

cura/ConvexHullDecorator.py

@@ -253,14 +253,11 @@ class ConvexHullDecorator(SceneNodeDecorator):
 
     ##  Offset the convex hull with settings that influence the collision area.
     #
-    #   This also applies a minimum offset of 0.5mm, because of edge cases due
-    #   to the rounding we apply.
-    #
     #   \param convex_hull Polygon of the original convex hull.
     #   \return New Polygon instance that is offset with everything that
     #   influences the collision area.
     def _offsetHull(self, convex_hull):
-        horizontal_expansion = max(0.5, self._getSettingProperty("xy_offset", "value"))
+        horizontal_expansion = self._getSettingProperty("xy_offset", "value")
         expansion_polygon = Polygon(numpy.array([
             [-horizontal_expansion, -horizontal_expansion],
             [-horizontal_expansion, horizontal_expansion],