Revert #1682 (three-axis milling) (#1715)

Thanks @bherbruck.

crates/kernel/src/lib.rs

@@ -172,7 +172,7 @@ pub use step_in::{
 };
 pub use step_out::{ExportBody, ExportProduct, StepHeader, step_export_bodies, step_export_products};
 pub use surface_extend::{ExtendLimit, ExtendMode, ExtendOptions, extend_surface};
-pub use surface_kind::{EdgeCircle, FaceSurface, edge_circle, face_surface, hole_axis};
+pub use surface_kind::{EdgeCircle, FaceSurface, edge_circle, face_surface};
 pub use surface_offset::offset_surface;
 pub use surface_ruled::{Ruled, RuledCorners, RuledMode, ruled_surface};
 pub use surface_untrim::{UntrimHoles, untrim};