Simplify extrapolate code

Author: urfeex

resources/external_control.urscript

@@ -149,10 +149,7 @@ end
 
 def extrapolate():
   cmd_servo_q_last = cmd_servo_q
-  local vel = get_target_joint_speeds()
-  local diff = [vel[0] * steptime, vel[1] * steptime, vel[2] * steptime, vel[3] * steptime, vel[4] * steptime, vel[5] * steptime]
-  cmd_servo_q = [cmd_servo_q[0] + diff[0], cmd_servo_q[1] + diff[1], cmd_servo_q[2] + diff[2], cmd_servo_q[3] + diff[3], cmd_servo_q[4] + diff[4], cmd_servo_q[5] + diff[5]]
-
+  cmd_servo_q = cmd_servo_q + (get_target_joint_speeds() * steptime)
   return cmd_servo_q
 end