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

variants/sensecap_solar/platformio.ini

@@ -10,7 +10,6 @@ build_flags = ${nrf52_base.build_flags}
   -I src/helpers/nrf52
   -UENV_INCLUDE_GPS
   -D NRF52_PLATFORM=1
-  -D USE_SX1262
   -D RADIO_CLASS=CustomSX1262
   -D WRAPPER_CLASS=CustomSX1262Wrapper
   -D P_LORA_TX_LED=12