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

variants/thinknode_m5/platformio.ini

@@ -32,7 +32,6 @@ build_flags = ${esp32_base.build_flags}
   -D SX126X_DIO2_AS_RF_SWITCH=true
   -D SX126X_DIO3_TCXO_VOLTAGE=3.3
   -D SX126X_CURRENT_LIMIT=140
-  -D USE_SX1262
   -D RADIO_CLASS=CustomSX1262
   -D WRAPPER_CLASS=CustomSX1262Wrapper
   -D LORA_TX_POWER=22