Update routing internal doc

ortools/constraint_solver/doc/CP.md

@@ -104,6 +104,7 @@ def main():
   print('Problem solved in ', solver.WallTime(), 'ms')
   print('Memory usage: ', pywrapcp.Solver.MemoryUsage(), 'bytes')
 
+
 if __name__ == '__main__':
   main()
 ```

ortools/constraint_solver/doc/ROUTING.md

@@ -116,6 +116,7 @@ def main():
     from_node = int(manager.IndexToNode(from_index))
     to_node = int(manager.IndexToNode(to_index))
     return abs(to_node - from_node)
+
   transit_callback_index = routing.RegisterTransitCallback(distance_callback)
 
   # Define cost of each arc.