Checkbox checked state isn't reflecting checked state as expected

[elliott-joo]

When creating a checkbox with the isSelected prop, I'm expecting it to be the single source of truth, but it seems that the checkbox has its own local state, that toggles the checked state.

To replicate:

• Create checkbox with isSelected={true}
• Checkbox does successfully render initially with a selected checkbox
• Click the checkbox
• Expecting the checkbox to not be checked, as the passed prop is still true

Not sure if this is as intended, but it gets in the way when we don't want the checkbox to behave on its own, such as when the checkbox checked state shouldn't occur until a popup is confirmed.