codal_app: Enable the Utility Service in BLE Pairing Mode.

This service enables datalog access to the apps, to be able to
view the logged data without a computer.

This flag enables the service in pairing mode only and should
have no effect when running MicroPython.

src/codal_app/codal.json

@@ -12,6 +12,7 @@
         "MICROBIT_BLE_PAIRING_MODE": 1,
         "MICROBIT_BLE_PARTIAL_FLASHING" : 1,
         "MICROBIT_BLE_SECURITY_MODE": 2,
+        "MICROBIT_BLE_UTILITY_SERVICE_PAIRING": 1,
         "MICROBIT_USB_SERIAL_WAKE": 1,
         "LEVEL_DETECTOR_SPL_8BIT_000_POINT": 52.0 
     },