Simplify choice of cells to un-carve while enforcing manifoldness

This combinatorial choice seemed like a good idea, but it can have
nasty cascading effects, adding very large tetrahedra. See this
issue: https://github.com/CGAL/cgal/issues/7625

In the end, the only thing we care about is small volumes being added.

I keep the artificial vertex for now, but I am not fully convinced
these should be actually kept too.

Alpha_wrap_3/include/CGAL/Alpha_wrap_3/internal/Alpha_wrap_3.h

@@ -1445,11 +1445,6 @@ private:
         if(has_artificial_vertex(r))
           return true;
 
-        const int l_bf_count = count_boundary_facets(l, v);
-        const int r_bf_count = count_boundary_facets(r, v);
-        if(l_bf_count != r_bf_count)
-          return l_bf_count > r_bf_count;
-
         return sq_longest_edge(l) < sq_longest_edge(r);
       };