Remove misleading docs.

pid_controller/src/pid_controller.cpp

@@ -25,21 +25,6 @@
 #include "control_msgs/msg/single_dof_state.hpp"
 #include "controller_interface/helpers.hpp"
 
-// The main knowledge could be with regard to the input (reference/state) and output (command)
-// interfaces and their physical meaning, for example:
-//
-// reference/state POSITION; command VELOCITY --> PI CONTROLLER
-// reference/state VELOCITY; command ACCELERATION --> PI CONTROLLER
-//
-// reference/state VELOCITY; command POSITION --> PD CONTROLLER
-// reference/state ACCELERATION; command VELOCITY --> PD CONTROLLER
-//
-// reference/state POSITION; command POSITION --> PID CONTROLLER
-// reference/state VELOCITY; command VELOCITY --> PID CONTROLLER
-// reference/state ACCELERATION; command ACCELERATION --> PID CONTROLLER
-// reference/state EFFORT; command EFFORT --> PID CONTROLLER
-//
-
 namespace
 {  // utility