[vpr][place] remove get_net_wirelength_from_layer_bb_ from netcosthandler class

Author: amin1377

vpr/src/place/net_cost_handler.h

@@ -508,14 +508,6 @@ class NetCostHandler {
      */
     double get_net_per_layer_bb_cost_(ClusterNetId net_id, bool use_ts);
 
-    /**
-     * @brief Given the per-layer BB, calculate the wire-length estimate of the net on each layer
-     * and return the sum of the lengths
-     * @param net_id ID of the net which wirelength estimate is requested
-     * @return Wirelength estimate of the net
-     */
-    double get_net_wirelength_from_layer_bb_(ClusterNetId net_id);
-
     /**
      * @brief Computes the inverse of average channel width for horizontal and
      * vertical channels within a bounding box.