AP_Tuning: removed chans 1 to 4 from TUNE_CHAN choices

libraries/AP_Tuning/AP_Tuning.cpp

@@ -9,7 +9,7 @@ const AP_Param::GroupInfo AP_Tuning::var_info[] = {
     // @Param: CHAN
     // @DisplayName: Transmitter tuning channel
     // @Description: This sets the channel for transmitter tuning. This should be connected to a knob or slider on your transmitter. It needs to be setup to use the PWM range given by TUNE_CHAN_MIN to TUNE_CHAN_MAX
-    // @Values: 0:Disable,1:Chan1,2:Chan3,3:Chan3,4:Chan4,5:Chan5,6:Chan6,7:Chan7,8:Chan8,9:Chan9,10:Chan10,11:Chan11,12:Chan12,13:Chan13,14:Chan14,15:Chan15,16:Chan16
+    // @Values: 0:Disable,5:Chan5,6:Chan6,7:Chan7,8:Chan8,9:Chan9,10:Chan10,11:Chan11,12:Chan12,13:Chan13,14:Chan14,15:Chan15,16:Chan16
     // @User: Standard
     AP_GROUPINFO("CHAN", 1, AP_Tuning, channel, 0),