codal_app: Update codal-microbit-v2 to v0.2.42-hotfix.1.

Only change is:
- Removes a small delay in the emoji synth to allow HLLs to run
  correctly

This is to fix:
#124

src/codal_app/codal.json

@@ -2,7 +2,7 @@
     "target": {
         "name": "codal-microbit-v2",
         "url": "https://github.com/lancaster-university/codal-microbit-v2",
-        "branch": "v0.2.42",
+        "branch": "v0.2.42-hotfix.1",
         "type": "git",
         "test_ignore": true
     } ,