Fix bore cube/cylinder junction shelf in cap

Cube bore right edge was at CAP_ENGAGE - CAP_WALL, where the cylinder
hasn't yet reached full bore height, leaving a ~0.09 mm shelf top and
bottom. Extend the cube to CAP_ENGAGE - _bore_r (cylinder center),
where the cylinder is exactly full-height, eliminating the step.

cable_cap.scad

@@ -192,7 +192,7 @@ module cable_cap() {
 
         // Rounded bore
         translate([-0.01, CAP_WALL, CAP_WALL])
-            cube([CAP_ENGAGE - CAP_WALL + 0.01, _cap_bore_w, _bore_h]);
+            cube([CAP_ENGAGE - _bore_r + 0.01, _cap_bore_w, _bore_h]);
         translate([CAP_ENGAGE - _bore_r, _cap_bore_w, _cap_bore_h - _bore_r])
             rotate([90,0,0])
                 cylinder(h=_cap_bore_w - CAP_WALL, r=_bore_r);