Remove unused function; we only need to support 3rd-order tensors.
Remove unused function; we only need to support 3rd-order tensors.

darcyliu/mlpack,stereomatchingkiss/mlpack,theranger/mlpack,ajjl/mlpack,erubboli/mlpack,ranjan1990/mlpack,theranger/mlpack,BookChan/mlpack,lezorich/mlpack,theranger/mlpack,stereomatchingkiss/mlpack,BookChan/mlpack,stereomatchingkiss/mlpack,darcyliu/mlpack,ranjan1990/mlpack,palashahuja/mlpack,ersanliqiao/mlpack,lezorich/mlpack,ajjl/mlpack,ranjan1990/mlpack,BookChan/mlpack,palashahuja/mlpack,ersanliqiao/mlpack,palashahuja/mlpack,lezorich/mlpack,darcyliu/mlpack,ajjl/mlpack,erubboli/mlpack,erubboli/mlpack,ersanliqiao/mlpack