Default button polarity to active-LOW across all firmware types

Nearly all LoRa boards use a boot button that pulls to ground when
pressed.

variants/wio-e5-mini/platformio.ini

@@ -9,7 +9,6 @@ build_flags = ${stm32_base.build_flags}
   -D RX_BOOSTED_GAIN=true
   -D P_LORA_TX_LED=LED_RED
   -D PIN_USER_BTN=USER_BTN
-  -D USER_BTN_PRESSED=LOW
   -I variants/wio-e5-mini
 build_src_filter = ${stm32_base.build_src_filter}
   +<../variants/wio-e5-mini>