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

Thanks @bherbruck.

crates/kernel/src/surface_kind.rs

@@ -165,21 +165,6 @@ impl FaceSurface {
     }
 }
 
-/// An inward cylindrical face's axis and radius. The caller still verifies the
-/// machined result against the complete target, including trimmed face bounds.
-pub fn hole_axis(b: &Body, face: usize, tolerance: f64) -> crate::Result<(Vec3, Vec3, f64)> {
-    if !tolerance.is_finite() || tolerance <= 0. {
-        return Err(crate::KernelError::Invalid("invalid hole tolerance".into()));
-    }
-    crate::guard("hole face axis", || {
-        let f = b.solid.face_iter().nth(face).ok_or_else(|| crate::KernelError::Invalid("hole face no longer exists".into()))?;
-        match surf_of(f, tolerance) {
-            Some(Surf::Cylinder { o, a, r, convex: false }) => Ok((o, a, r)),
-            _ => Err(crate::KernelError::Invalid("select an inward cylindrical hole face".into())),
-        }
-    })
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;