Copter: update "CH6 tuning" comments

ArduCopter/Copter.cpp

@@ -659,7 +659,7 @@ void Copter::three_hz_loop()
     // check for deadreckoning failsafe
     failsafe_deadreckon_check();
 
-    // update ch6 in flight tuning
+    //update transmitter based in flight tuning
     tuning();
 
     // check if avoidance should be enabled based on alt

ArduCopter/mode_circle.cpp

@@ -68,7 +68,7 @@ void ModeCircle::run()
         }
 
         // update the orbicular rate target based on pilot roll stick inputs
-        // skip if using CH6 tuning knob for circle rate
+        // skip if using transmitter based tuning knob for circle rate
         if (g.radio_tuning != TUNING_CIRCLE_RATE) {
             const float roll_stick = channel_roll->norm_input_dz();         // roll stick normalized -1 to 1