Upgrade to @microbit/ui@0.1.0-alpha.24

Brings in the unpositioned body fixing react-aria's top-placed
overlays on scrolled pages. No app-side changes needed: the shell
pins body to the viewport, so nothing here ever showed the bug.

Author: microbit-matt-hillsdon

package-lock.json

@@ -21,7 +21,7 @@
     "@codemirror/view": "^6.26.3",
     "@microbit/microbit-connection": "^1.0.0",
     "@microbit/microbit-fs": "^0.10.0",
-    "@microbit/ui": "0.1.0-alpha.23",
+    "@microbit/ui": "0.1.0-alpha.24",
     "@sanity/block-content-to-react": "^3.0.0",
     "@sanity/image-url": "^1.0.1",
     "@testing-library/jest-dom": "^5.14.1",