codal_app: Update codal-microbit-v2 to v0.2.31.

Changes are:

codal-microbit-v2:
- update bootloader to not perform a CRC of the application flash on boot
    - This fixes an issue where the bootloader got stuck after a BLE flash
- add check for old bootloader settings and updates them if needed
- multiple updates to the data logging HTML viewer
- parameterisation of I2C storage RX/TX retransmission counters

codal-core:
- no changes

codal-nrf52:
- no changes

src/codal_app/codal.json

@@ -2,7 +2,7 @@
     "target": {
         "name": "codal-microbit-v2",
         "url": "https://github.com/lancaster-university/codal-microbit-v2",
-        "branch": "v0.2.29",
+        "branch": "v0.2.31",
         "type": "git",
         "test_ignore": true
     } ,