Remove unused RX boosted gain mode functions and related preprocessor directives across multiple variants

variants/thinknode_m6/target.cpp

@@ -48,12 +48,3 @@ mesh::LocalIdentity radio_new_identity() {
   return mesh::LocalIdentity(&rng);  // create new random identity
 }
 
-#if defined(USE_SX1262) || defined(USE_SX1268)
-void radio_set_rx_boosted_gain_mode(bool rxbgm) {
-  radio.setRxBoostedGainMode(rxbgm);
-}
-
-bool radio_get_rx_boosted_gain_mode() {
-  return radio.getRxBoostedGainMode();
-}
-#endif