[docs] Migrate Radio demos to emotion

[vicasas]

• I have followed (at least) the PR section of the contributing guide.

The following demos of the Radio component were migrated:

• Error radio
• Customized radio
• useRadioGroup

Related to #16947

[vicasas]

@oliviertassinari Is it correct to do this for styles that make sense? Is there another way?

const StyledFormControlLabel = styled((props: StyledFormControlLabelProps) => (
  <FormControlLabel {...props} />
))(({ theme, checked }) => ({
  '.MuiFormControlLabel-label': checked && {
    color: theme.palette.secondary.main,
  },
}));

[mui-pr-bot]

No bundle size changes

Generated by 🚫 dangerJS against efc04ca

[vicasas]

This failed for timeout. Run again CI please.

[oliviertassinari]

On https://deploy-preview-25396--material-ui.netlify.app/components/radio-buttons/#customized-radios, the focus-visible state is broken

[oliviertassinari]

I have used the fix of the checkbox PR and applied it here. We are good :)

[vicasas]

@oliviertassinari I could not replicate it here, my day was full. Thanks for the help!