codal_app: Update codal-microbit-v2 to v0.2.29.

Changes are:

codal-microbit-v2:
- improvements to MicroBitLog
- make private pin variable a pointer, to fix pins becoming other pins
- deep sleep support
- fix memory leak in MicroBitAudio::setSleep()/enable()

codal-core:
- introduce framework for power efficient deep sleep

codal-nrf52:
- update drivers to support deep sleep mode

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

src/codal_app/codal.json

@@ -2,7 +2,7 @@
     "target": {
         "name": "codal-microbit-v2",
         "url": "https://github.com/lancaster-university/codal-microbit-v2",
-        "branch": "v0.2.26",
+        "branch": "v0.2.29",
         "type": "git",
         "test_ignore": true
     } ,