M3 Checkboxes should have a border radius of `2.0` - [spec](https://m3.material.io/components/checkbox/specs). However, this is currently set to `1.0` - [`checkbox.dart`](https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/material/checkbox.dart). This should be updated.