Bug: input[type="radio"] controlled value can get out-of-sync

React version: 16.13.1 and 17.0.0-alpha.0-2d131d782 ## Steps To Reproduce 1. Render two `input[type="radio"][name="radio"]`: one is checked, one isn't 2. Get warning about passing `onChange` or `readOnly` 3. Add empty `onChange` to both Link to code example: - [React 16 repro](https://codesandbox.io/s/react-16-radio-cannot-be-read-only-z9ldc) - [React 17 repro](https://codesandbox.io/s/react-17-radio-cannot-be-read-only-forked-r6m9r) - [React 18 repro](https://codesandbox.io/s/react-18-radio-cannot-be-read-only-forked-7j9ckd) ## The current behavior  1. React recommends `readOnly` for `input[type="radio"]` even though this isn't supported natively (though React could polyfill it) 2. After looping through the radios once with arrow key navigation the checked state changes ## The expected behavior Arrow key navigation shouldn't break out of the controlled value. It's debateable whether React should recommend `readOnly` when this isn't a standard attribute like `readOnly` for `<input type="text" />`.