Code eval tool: Change the alert for when a user is deleting a criteria

[srietkerk]

When a user is deleting a criteria from their checklist, they get an alert asking if they're sure they want to delete the criteria. The alert is not the prettiest.

To Reproduce Steps to reproduce the behavior:

1. Go to https://makecode.microbit.org/beta---eval
2. Make a checklist
3. Add criteria to that checklist
4. Delete a criterium
5. See the alert

Not sure if we want to just use a pop-up/modal here instead to make it look like expected behavior or if we just want to remove the alert and not give a pop-up here because deleting a criteria is not super detrimental to the user.