fix(sensecap_solar): set P_LORA_TX_LED to 12 after LED remap

Align TX activity LED with LED_BLUE / variant.h after LED definition
and power-button pin mapping changes.

variants/sensecap_solar/platformio.ini

@@ -13,7 +13,7 @@ build_flags = ${nrf52_base.build_flags}
   -D NRF52_POWER_MANAGEMENT
   -D RADIO_CLASS=CustomSX1262
   -D WRAPPER_CLASS=CustomSX1262Wrapper
-  -D P_LORA_TX_LED=11
+  -D P_LORA_TX_LED=12
   -D P_LORA_DIO_1=1
   -D P_LORA_RESET=2
   -D P_LORA_BUSY=3