[nrfconnect] Fix setting pincode based on kconfig. (#23172)

Currently the CONFIG_CHIP_DEVICE_PAIRING_PASSCODE is used for
setting pincode, but such symbol doesn't exist anymore.
Used correct CONFIG_CHIP_DEVICE_SPAKE2_PASSCODE symbol instead.

Author: kkasperczyk-no

src/platform/nrfconnect/CHIPDevicePlatformConfig.h

@@ -40,7 +40,7 @@
 #endif
 
 #ifndef CHIP_DEVICE_CONFIG_USE_TEST_SETUP_PIN_CODE
-#define CHIP_DEVICE_CONFIG_USE_TEST_SETUP_PIN_CODE CONFIG_CHIP_DEVICE_PAIRING_PASSCODE
+#define CHIP_DEVICE_CONFIG_USE_TEST_SETUP_PIN_CODE CONFIG_CHIP_DEVICE_SPAKE2_PASSCODE
 #endif
 
 #ifndef CHIP_DEVICE_CONFIG_USE_TEST_SETUP_DISCRIMINATOR