MDC-based checkbox & radio click targets are too small

[jelbourn]

Our MDC-based checkbox and radio have click targets at 40px × 40px instead of 48 × 48px. Slide-toggle is already good here.

Fix for checkbox is already open in #22892

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}