fix(boards): restore Station G2 GPS UART pin mapping

Match MCU RX=7 / TX=15 used by G3 and Meshtastic; the prior
values were an accidental revert of 0920dc66.

variants/station_g2/platformio.ini

@@ -23,8 +23,8 @@ build_flags =
   -D PIN_BOARD_SDA=5
   -D PIN_BOARD_SCL=6
   -D PIN_USER_BTN=38
-  -D PIN_GPS_RX=7
-  -D PIN_GPS_TX=15
+  -D PIN_GPS_RX=15
+  -D PIN_GPS_TX=7
   -D SX126X_DIO2_AS_RF_SWITCH=true
   -D SX126X_DIO3_TCXO_VOLTAGE=1.8
   -D SX126X_CURRENT_LIMIT=140